A Ukrainian man has gone on trial in Hamburg accused of blowing up Russia’s Nord Stream gas pipelines to Germany, four years after one of the most dramatic acts of sabotage in modern European history.

Prosecutors say Serhii Kuznetsov played a leading role in a team of saboteurs that destroyed the pipelines, accusing him of a war crime. His defence has called for the case to be dismissed.

The case is highly sensitive in Germany, one of Ukraine’s closest allies since Russia launched its full-scale invasion in February 2022, seven months before the attacks took place.

Extradited to Germany last year, Kuznetsov denies the charges, as does a second suspect who is fighting extradition from Croatia.

Kuznetsov became the first suspect to go on trial for the blasts on Wednesday morning, and a packed public gallery looked on as he entered the courtroom, appearing relaxed.

He even smiled at times, including during initial exchanges where he spoke to confirm personal details such as his name and place of birth.

He had previously only been identified by German prosecutors as Serhii K and pictured with his face blurred, before the court lifted an anonymity order on Wednesday.

Kuznetsov, 50, wore a pair of headphones and appeared to listen intently to a translation of proceedings in Ukrainian, as the prosecution read out the charges against him of ordering divers and an explosive expert to attack civilian infrastructure.

The defence outlined their case, telling the court that only circumstantial evidence had emerged in the four years since the Nord Stream blasts.

“[Prosecutors] made a thorough investigation of four years,” Italian defence lawyer Nicola Canestrini told the BBC outside the courtroom. “They did not find one single witness, they did not find no forensics, no DNA, no fingerprints – nothing!”