Russia is rushing to repair the bridge connecting occupied Crimea to Russia after a major blast on Saturday, in an attempt to downplay the attack.

Suburban train lines are scheduled to start running again on the Kerch Bridge as of 7 p.m. local time, according to a message from the Russian Transport Ministry posted on Telegram Sunday. Long-distance freight and passenger trains on the bridge already “are moving according to the standard schedule,” the ministry said.

The fiery explosion Saturday morning marked a huge symbolic blow against Russian President Vladimir Putin, who grabbed Crimea from Ukraine in 2014 and started building the bridge connecting the Ukrainian peninsula to Russia that same year.

“This incident will likely touch President Putin closely,” the U.K. Ministry of Defense said in analysis published on Sunday, since the blast happened “hours after his 70th birthday” and his childhood friend Arkady Rotenberg built the bridge.

Putin tightened security for the bridge after Saturday’s explosion, and he ordered a government commission to investigate the damage. The initial report from Moscow’s inspection of the bridge is due later Sunday.

Meanwhile, the Russian Foreign Ministry appeared to be downplaying the blow as it tweeted a video of the Kerch Bridge with traffic flowing. Despite Moscow’s message of business as usual, the U.K.’s Defense Ministry said that transport “capacity will be seriously degraded” on the bridge.

“The extent of damage to the rail crossing is uncertain, but any serious disruption to its capacity will highly likely have a significant impact on Russia’s already strained ability to sustain its forces in southern Ukraine,” the U.K. ministry said.

Russia’s Ministry of Transport wrote on Telegram Sunday that vehicles containing perishable goods would be given priority on ferries crossing the Kerch Strait.

The Ukrainian government so far hasn’t been commenting about the origins of the apparent bombing. Ukraine’s Deputy Foreign Minister Emine Dzheppar posted a picture of the collapsed bridge section on Saturday with the hashtag #CrimeaIsUkraine.

Over the past few weeks, Ukraine has been leading a counteroffensive against Russia and regaining territory and towns held by Moscow. Kyiv is now asking for more Western weapons, including air defense systems. The Kremlin signalled on Sunday that if the West were to provide Ukraine with heavier long-distance arms, Russia would retaliate.

“Deliveries of long-range or more powerful weapons to Kyiv” would cross Russia’s “red lines,” Russian foreign affairs official Aleksey Polishchuk told the country’s state-owned news agency TASS on Sunday.

Ukrainian Foreign Minister Dmytro Kuleba renewed the call for additional defensive systems on Sunday, after at least 17 people were reported killed overnight by Russian shelling on the city of Zaporizhzhia.

“Russia continues its missile terror against civilians in Zaporizhzhia,” Kuleba said in a tweet. “We urgently need more modern air and missile defense systems to save innocent lives. I urge partners to speed up deliveries.”

The attack on the Kerch bridge to Crimea stunned both Ukrainians and Russians with its scale and ingenuity, leaving experts wondering who was responsible for the attack and how it was achieved.

From truck bomb to underwater attack, military experts and analysts have put forward several theories on what caused Saturday’s explosion on the 12-mile road and rail link to the peninsula annexed by Russian president Vladimir Putin in 2014, though their findings are not conclusive.

“It is too early to be definitive about the cause of the blast based on the publicly available information,” said NR Jenzen-Jones, an arms and munitions specialist at Armament Research Services.

The bridge has been an obsession of Ukrainians for as long as it had been one of Putin’s signature infrastructure projects. Viktor Andrusiv, who was an adviser until July at Kyiv’s interior ministry, said he had taken part in a task force with the military to research viable options for destroying it.

“It’s not an easy task, not at all,” said Andrusiv, who has publicly demanded the bridge be destroyed for months. “It’s a very well-protected object — from the air, from the sea, from the ground.”

Was a missile used?

Most defence experts think this type of attack was unlikely. The bridge was out of the reach of Kyiv’s US-supplied Himars, a medium-range guided artillery rocket system, and American defence officials had warned that they were not to be used on the bridge, according to a US and a Ukrainian official.

But two homegrown Neptune anti-ship missiles were used to destroy the Moskva, the flagship of Russia’s Black Sea fleet, in April, indicating Ukraine’s ability to effectively use this type of airborne attack against Russia, albeit at shorter distances.

Those surprisingly accurate hits suggest that western allies may be providing technical help to fine-tune Ukrainian weapons, analysts say. They have so far turned down Ukrainian requests for longer-range US-made missiles that can be fired from the Himars.

Satellite image shows damage to the Kerch bridge © Maxar Technologies/AP

“Check for cloudy weather — thunder, rain?” said a western official, when asked what brought down a section of the bridge. This was perhaps a cryptic reference to the Grim2, a Ukrainian missile with a theoretical range of up to 500km that has been under development for decades.

Grim, and the missile’s earlier name, Grom, are Ukrainian words for thunder. Ukrainian president Volodymyr Zelenskyy also described the weather in Crimea as “cloudy” in his nightly broadcast on Saturday.

Did a truck bomb cause the damage?

The most popular theory was a bomb blast from a white truck identified in online footage. “There was something in the truck that exploded,” said a structural engineer, now in a specialised branch of the Ukrainian military, who analysed the videos. “Something special.”

A fireball appeared on cameras just as the truck was parallel to a train carrying fuel, adding to the conflagration that has reduced traffic on the bridge to single lanes for vehicles and trains. If it was a truck bomb, he said it could indicate that it was followed either from the air or by another vehicle whose pilot or driver could relay the optimal time to detonate. Russian investigators say three people were killed in the explosion, but it is not known whether they were participants or innocent bystanders.

Serhiy Kuzan, an adviser to the Ukrainian defence ministry, disagreed, noting two adjoining strikes in his analysis of the publicly available footage. “We see that the support construction of the roadway bridge is destroyed in two locations,” he said, adding that blaming it on a truck allows Russia to define it as terrorism rather than a targeted military strike.

But Andrusiv reached the same conclusion as the structural engineer-turned-soldier. “It was a truck bomb, and quite likely, the truck was also carrying agricultural chemicals,” he said, suggesting that the size of the explosion was amplified by the truck’s contents.

Is an underwater attack plausible?

The graininess of available footage has resulted in various, less plausible theories. Some videos appeared to show a vessel travelling under the bridge at the time of the explosion. “Possibly a remote-controlled boat-borne explosive with a sensor for detonation when it passed under a structure?” OSINT Amateur, a small open-source investigative group, wrote on Twitter.

However, a photograph of the underside of the collapsed bridge, also shared on social media, showed no burn marks or crumpled metal that would indicate a blast travelling up from the water’s surface.

Photos of an unmanned maritime drone washing up on the shores of Crimea were shared on social media earlier this year, indicating that Ukraine may be able to carry out a submersible strike.

Who carried out the strike?

Military experts believe Ukraine’s intelligence services are the most likely branch of Kyiv’s security apparatus to have carried out the assault.

Andrusiv said the joint task force had considered missiles, unmanned aerial vehicles, underwater drones, stealth boats and a truck bomb. Ukrainian missiles did not have precision at that range, and the other options needed specialised weapons that they didn’t have. They did not reach a conclusive assessment.

One western adviser described the intelligence services as having combined Nato-like capabilities with Mossad-style mystique for their covert operations during the seven-month-long conflict with Russia. These have included special operations deep in occupied regions using partisan and elite forces.

But the strategy of disinformation, evasiveness and counteraccusation from Ukraine and its allies about the audacious attack allows them to sow disinformation or at least confusion — and keeps the Kremlin, as well as influential military bloggers and hawkish television presenters, guessing at Ukraine’s capabilities.

Mykhailo Podolyak, an adviser to Zelenskyy, even suggested that the infighting between different power centres in Moscow was behind the attack. “This is a concrete material manifestation of the conflict between the [intelligence services] on the one hand and the [military] on the other,” he told the Financial Times.

As evidence, he pointed to the fact that the truck seen in the videos was driving from Russia to Crimea. “The logistics of the detonation . . . all this clearly points to the Russian trail,” he said. Russia’s president late on Sunday said there was “no doubt” that Ukraine was behind the explosion, calling it a terrorist attack.

Jenzen-Jones said the signal sent by the strike was stronger than its physical impact since only one of the two rail lanes appears to be destroyed.

“If the damage to the Kerch bridge did indeed result from a Ukrainian strike, it represents a propaganda victory more than an operational one.”

The huge explosion on the Crimea bridge shortly before dawn on Saturday severely curtailed road and rail traffic along an important artery – both civilian and military – at a critical moment in Russia’s campaign in Ukraine.

At first sight, it was another embarrassment – even humiliation – for the Russian state, still reeling from battlefield setbacks in Kharkiv, Donetsk and, more recently, in Kherson in the south.

But by Monday the bridge attack had also become the Kremlin’s justification for a sudden blitz of missile attacks across Ukraine. By midday, according to Ukrainian authorities, some 80 missiles and rockets had been fired at infrastructure in a dozen cities – and Russian officials were promising more to come.

In the hours after the bridge explosion, Russian investigators fastened onto one explanation for the blast: It was a terrorist attack using a massive explosive charge hidden in a truck and then detonated as the vehicle crossed the bridge toward Crimea.

Russian President Vladimir Putin picked up the theme on Monday, saying Kyiv had “put itself on a par with the most odious terrorist groups,” which had prompted the subsequent “massive strike with precision-guided weapons on Ukrainian infrastructure – energy infrastructure, military command and communications.”

“It is simply impossible to leave the crimes of the Kyiv regime unanswered,” he said.

Putin went on: “In terms of the further act of terrorism on the territory of Russia, the Russian reply will be harsh and will be corresponding to the level of threat to the Russian Federation, have no doubt about it.”

The explosion, Moscow’s version of what happened and the absence of any Ukrainian acknowledgement for carrying it out, has set off a firestorm of theorizing about what caused it and who was responsible.

The Kerch bridge is about 150 miles from the nearest Ukrainian positions, and well beyond the range of weapons provided by the West. But Ukrainian drones were reported to have approached the area in the summer, setting off air defense measures.

Some analysts unconvinced by the truck bomb narrative suggested a missile or missiles fired by drones may have been responsible, or that an underwater sabotage team had fixed charges to the bridge’s support structure.

Images and video from the scene were inconclusive. As the truck identified by the Russians crosses the bridge and begins to ascend to its highest point, it is engulfed in a massive explosion.

The Russian Investigative Committee, charged with finding out what caused the explosion, quickly identified the vehicle. Surveillance video emerged of the truck, with its distinct scarlet cab, at a checkpoint before it enters the bridge. It receives a cursory inspection; the driver – in a short-sleeve shirt – is seen briefly closing the truck’s rear doors.

But it’s unclear how a truck bomb would have caused two separate spans of the westbound lanes to collapse into the Kerch Strait. Additionally, the force of such a blast would have mostly gone upwards and outwards. Some analysts note that the way the spans collapsed imply the force of the blast came from below.

Chris Cobb-Smith, an analyst with the research group Forensic Architecture, is skeptical about the truck narrative. “It’s possible to blow a bridge by using explosives on the span but it takes a huge amount and needs ‘tamping’ – a huge weight of ballast on the charge to ensure the blast goes downwards,” he told CNN.

“I don’t believe a truck bomb could have caused this level of damage. This would have entailed a suicide bomber driver, unheard of in the context of this conflict.”

Cobb-Smith, a British army veteran, is also skeptical of a special forces operation. “There are accurate weapon systems that could achieve the aim of destroying the bridge without risking individuals.”

But he cautions: “To solve this I believe we need analysis of the bits of the bridge currently underwater. I still think this would have been easily achieved by a precision munition.”

On Sunday, the head of Russia’s Investigative Committee, Alexander Bastrykin, doubled down on the truck explanation.

Face-to-face with Putin in a well-choreographed exchange, Bastrykin said the truck had been in Bulgaria before traveling through Georgia, Armenia, North Ossetia and into Russia. (It would have also had to cross Turkey.)

“It was possible to identify suspects from among those who could prepare a terrorist attack, and people who operate on the territory of the Russian Federation,” Bastrykin said, referring to “citizens of foreign countries who helped prepare for this terrorist attack.”

The investigators reached an “unequivocal conclusion – this is a terrorist attack that was being prepared by the Ukrainian special services,” Bastrykin said.

A stern-faced Putin responded: “I see.” Notably, the president went on to say: “There is no doubt that this is a terrorist attack aimed at destroying the critical civilian infrastructure of the Russian Federation,” carried out by the special services of Ukraine.

On one level, the “act of terror” narrative would at least excuse the Russian military from having to explain why its multi-layered defenses around the bridge failed, despite Ukraine’s public assertions that it was a legitimate target. On another, it provides – through Moscow’s prism – the justification for the massive escalation of attacks on Ukrainian infrastructure.

Ukrainian intelligence claims those attacks were planned days before the Kerch explosion. Its defense intelligence agency said Monday that Russian military units had “received instructions from the Kremlin to prepare massive missile strikes on the civilian infrastructure of Ukraine on October 2 and 3.”

If it wasn’t the truck, what might have caused such an explosion? Cobb-Smith says a surface vessel of any sort should and would have been detected.

Some analysts have suggested that the explosion could have come from beneath the bridge; others think satellite images indicate the impact was from above and came from the north.

Ultimately, according to Cobb-Smith and other experts, there is insufficient video evidence to confirm what happened at Kerch.

There is no doubt that the Ukrainians have seen Kerch as a legitimate, even necessary, target.

Back in June Dmytro Marchenko, a Ukrainian Maj. Gen. Major General in the south of the country, said the Kerch bridge was the “number one target.”

Marchenko told Radio Liberty: “This is no secret to their military or our military. Neither for their civilians nor for our civilians. This will be the number one target to hit. It’s as if the main gut tightening reserves just have to be cut off. As soon as this intestine is cut off, they will begin to panic.”

But Ukrainian officials have been tight-lipped about Saturday’s explosion, welcoming the crippling of the bridge (somewhat prematurely given that limited road and rail traffic resumed within 24 hours) without acknowledging involvement.

They took the same approach with the sinking of the Russian battleship Moskva. It was weeks before any official acknowledgement emerged.

Some Ukrainian officials put the Kerch explosion down to an internal power struggle between Russia’s Security Service and Defense Ministry, without offering any evidence.

Mykhailo Podolyak, an adviser to President Zelensky’s chief of staff, said Saturday that “the logistics of the detonation, the synchronization with the fuel echelon [the rail wagons carrying fuel], the volume of the destroyed road surface – all this clearly points to the Russian trail.”

The cause of the Kerch blast, and its perpetrator, remain open questions. They may do for some time to come. But there is no doubt that the conflict in Ukraine has moved to yet another level, with Russia now embarked on a relentless assault against Ukraine’s power and communications networks, and Ukrainian officials swearing revenge for every missile.

— Ministry of Defence 🇬🇧 (@DefenceHQ) October 10, 2022

• The latest death toll update comes from the Ukrainian State Emergency Service and confirms that at least 11 people have died with another 64 injured.

  Five were killed in Kyiv, where a series of blasts struck a playground, a road and a building.

• The International Committee of the Red Cross has temporarily halted its work in Ukraine for security reasons.

  It comes after Russia fired missiles at multiple cities across Ukraine.

  “For security reasons, our teams have paused operations today,” a spokesperson said in an emailed response to a Reuters question.

• Denys Shmyhal said one of the “first targets” was a “children’s playground”, he said: “Unfortunately, people died.”

  Mr Shmyhal added: “As of 11am, 11 important infrastructure facilities in eight regions and the city of Kyiv were damaged. 

  “Now some areas are cut off. It is necessary to be prepared for temporary interruptions with light, water supply, and communication. 

  “The main goal of these war criminals is to sow panic, frighten, and leave Ukrainians without light and heat.”

• At least 10 people were killed and 60 wounded in Russian missile strikes across Ukraine, police said.

  Russia’s defence ministry said it had hit “all designated targets” in its massive missile attack on Ukrainian military, communications and energy infrastructure.

  President Volodymyr Zelensky accused Russia of trying to wipe his country “off the face of the earth” and his defence ministry vowed revenge for the attacks.

  Zelensky’s top general, Valeriy Zaluzhnyi, said Ukraine had shot down at least 41 Russian missiles of some 75 launched.

  Ukrainian Prime Minister Denys Shmygal said 11 infrastructure facilities in eight regions

• The Ukrainian ministry of defence wrote on Twitter: “So, russkies, you really think you can compensate for your impotence on the battlefield with missile strikes on peaceful cities?

  “You just don’t get it do you – your terrorist strikes only make us stronger.

  “We are coming after you.”

  So, russkies, you really think you can compensate for your impotence on the battlefield with missile strikes on peaceful cities? You just don’t get it do you – your terrorist strikes only make us stronger. We are coming after you.

  — Defense of Ukraine (@DefenceU) October 10, 2022

• Russian president Vladimir Putin will meet the head of the UN’s atomic energy agency Rafael Grossi in Russia’s second city Saint Petersburg on Tuesday, the Kremlin said.

  Their meeting comes after repeated shelling of Ukraine’s Moscow-held Zaporizhzhia nuclear power plant — Europe’s largest atomic facility — raised fears of an impending nuclear disaster.

• The Kremlin said explosions that rocked Kyiv on Monday were part of what it calls its “special military operation”.

  Several Ukrainian cities were left without power or water supplies after dozens of Russian missiles hit cities across the country on Monday morning.

  The multiple attacks are being seen as a revenge attack for the explosion on a key bridge linking Russia to the annexed Crimean peninsula over the weekend. 

• Mr Cleverly wrote: “Russia’s firing of missiles into civilian areas of Ukraine is unacceptable.

  “I communicated with Dmytro Kuleba this morning to reinforce the UK’s ongoing moral and practical support to Ukraine.

  “This is a demonstration of weakness by Putin, not strength.”

• The image below shows a car destroyed as a result of a rocket attack by Russian troops.

  The carnage took place overnight Zaporizhzhia, south-eastern Ukraine, as Russian forces launches attacks on eight regions.

  This included capital Kyiv, where a number of civilians were confirmed to have been killed by strikes.

  A car destroyed as a result of a rocket attack by Russian troops in the private sector of Zaporizhzhia, south-eastern Ukraine.

• Ukrainian president Volodymyr Zelenskyy has discussed a G7 meeting with German Chancellor Olaf Scholz today.

  On Twitter, he said: “Agreed with Chancellor Olaf Scholz of Germany holding presidency of G7 on an urgent meeting of the Group.

  “My speech is scheduled, in which I’ll tell about the terrorist attacks by [Russia Federation]. 

  “We also discussed the issue of increasing pressure on RF & aid in restoring damaged infrastructure.”