Nord Stream trial: How German police followed the evidence - to Ukraine

Serhii K appeared relaxed as he checked in to the glamping resort near Italy's Adriatic coast with his wife and young children.

Dressed in shorts, sandals and a dark baseball cap, the former Ukrainian Special Forces soldier strolled back and forth, chatting with the receptionist and dipping repeatedly into a bowl of free snacks.

But German police were already closing in on him.

After a painstaking investigation, they had concluded that Serhii K had commanded Europe's biggest act of sabotage in decades: a series of explosions in September 2022 deep beneath the Baltic Sea that ripped through the giant Nord Stream pipelines and ruptured the supply of Russian gas to Germany.

Next week, following his extradition to Germany and months in isolation in a high security prison, Serhii K will go on trial in Hamburg. He is charged with causing an explosion and a war crime – attacking civilian infrastructure – allegedly acting on behalf of "state agencies of Ukraine".

Both he and his country have denied any involvement.

Under Germany's privacy rules, he will be named during the trial only as Serhii K, but during extradition proceedings he was identified as Serhii Kuznetsov.

It was 02:03 am on 26 September 2022 when the first blast severed part of the Nord Stream pipelines, sending vast quantities of gas gushing through the surface of the Baltic Sea.

There were two further explosions targeting both Nord Stream 2 – not yet in action, but already full – and the original Nord Stream 1 that had supplied around half of Germany's annual demand for natural gas.

Both have been inoperable ever since.

Prosecutors say "high-performance explosives" were planted approximately 80m (260ft) below the surface: four devices weighing up to 27kg each, activated with timers.

They "strongly suspect" that Serhii K led a crew that included four deep-sea divers, using a rented yacht called Andromeda.

Once their complex, dangerous mission was done, the saboteurs slipped back into Ukraine unaware of the DNA evidence some had allegedly left on the boat.

As word of the blasts spread, experts and some governments initially rushed to the same conclusion: they blamed Moscow.

Russia had a history of hybrid attacks, after all, and of using its energy supplies for political pressure.

But as the airwaves filled with commentators citing "suspicious" Russian naval activity near the blast site, German police ignored the noise.

They went on following the forensic crumbs.

Eventually they led to Ukraine.

The case since built by investigators alleges that Serhii K entered Germany for the Nord Stream attack on a forged passport, likely issued by Ukraine's security services.

In the extradition files sent to Italy he is named as Serhii Kulinich.

That might explain why he looked so calm on his holiday in Italy.

He had been travelling widely, and without incident, for the past year. In a copy of his real passport seen by the BBC there are more than two dozen stamps from countries including France, Spain and Canada – all dated after the Nord Stream attacks.

But by 13 August 2025, Germany had identified its key suspect and this time, when Serhii K crossed into Poland, he was detected.

Italian police say the actual arrest warrant was only issued on 18 August after he had travelled south and left Poland, suggesting the Germans were not sure their neighbours would co-operate and detain him.

By the time his wife made a booking at La Pescaccia though, he was officially a "wanted" man. As soon as he showed his passport at check-in at the resort, the local carabinieri got an automatic alert.

Police arrived to make their arrest late that night, leading Serhii K away from the glamping site and his family in handcuffs.

None of the Nord Stream suspects have spoken publicly and no-one admits any role in the explosions.

But I have talked to some of the Ukrainians caught up in the case, and people close to them.

"Anyone who admits involvement in this mission, they're immediately a target for Russia," one source explained. "Whoever did it can never confirm that."

Nord Stream was a major investment and worth big money to Moscow in fuel sales. But it also made Germany and others dependent, giving Russia immense leverage over Europe.

That is why Ukraine, the US and Poland in particular all loathed it.

Another source I spoke to was "eaten alive by anxiety" over the investigation and baffled that Germany, a close ally of Ukraine, was even pursuing prosecution.

"Many Ukrainians believe that these pipelines, they helped Russia to fight so blowing them up was a good thing for our country," they pointed out.

The German prosecutor's office told me the justice system was outside of any politics. Sabotage is an offence against Germany's constitution.

Equally frustrating for the Ukrainians I met was their own government's silence.

"At the very minimum, he's a military man, so if there are any questions, they should be addressed to the state, not to him," a close contact of Serhii K complained.

Ahead of his extradition to Germany, his lawyer here in Italy told me his client had felt "abandoned".

Germany has a whole list of suspects, but only one other name has been revealed so far.

Volodymyr Zhuravlyov is currently fighting extradition from Croatia where he was arrested in August.

He was there as a consultant on a new thriller film about the Nord Stream blasts, though he denies any role in the real-life operation.

Travelling was a risky move, when he knew Germany was pursuing him.

Zhuravylov has lived in Warsaw with his family since just before Russia's full-scale invasion of Ukraine and has his own business there installing air conditioning.

He is also a keen and competent deep-sea diver.

But he is a civilian.

Last year, he was arrested in Warsaw on a warrant issued by Germany but a Polish judge refused to extradite him.

In a dramatic twist, he ruled instead that a Ukrainian attack on Nord Stream, if that was what happened, would be a "just" act in a "bloody and genocidal war".

As one source close to the case put it to me: "The Poles don't like Ukrainians, historically, but they hate Russians and Germans even more."

Croatia is a different matter.

The implications of this case reach far beyond the courthouse in Hamburg.

After a slow start, Germany is now Ukraine's biggest supplier of military aid. The far-right AfD party, currently riding high in the polls, has seized on the Nord Stream case to bolster its argument that support for Kyiv needs to stop.

It is awkward, at the very least, for the governments in both Berlin and Kyiv.

It also raises questions about what constitutes a legitimate military target: who can hit what, and where, outside an open war zone.

When asked about the explosions, President Zelensky has previously insisted that Ukraine "definitely didn't do that".

This week, a foreign ministry spokesman went further.

"I find it very unfortunate that this entire discussion has come to focus on who blew [the pipelines] up, rather than who built them," Heorhii Tykhyi told the BBC, forcefully.

He argued that the Nord Stream pipelines had "untied Russia's hands" to go to war, because it no longer needed that to transit Ukraine for its gas to reach Europe.

"Did we warn about this? We did," Tykhyi wanted to know. "Did anyone listen to us? No, no-one did."

Serhii K will shortly become the first suspect to face charges in this high profile trial.

Zhuravlyov's case could be merged, in theory, at a later date, though that would be complicated.

Those who know Serhii K call him a patriot.

He signed up to defend Ukraine when Russia invaded even though he had several children and was exempt - and fought until December 2023.

His military ID shows that he was still in active service when the pipelines were blown up, meaning someone in Ukraine's military command knew exactly where he was and what he was doing.

They are not saying, though.

And in court Serhii K himself will not say a word, either.

His legal team will argue that he is not authorised to reveal details of any activities as a soldier and produce sworn statements from two of his military superiors to back that up.

I am told one of them will be the man widely named as the mastermind of the entire Nord Stream plot.