German prosecutors say a Ukrainian man has been arrested in Italy on suspicion of blowing up the Nord Stream gas pipelines under the Baltic Sea, several months after the start of Russia’s full-scale invasion of Ukraine in 2022.

The man, identified only as Serhii K, was arrested in the province of Rimini and was part of a group who planted explosives under the Nord Stream 1 and Nord Stream 2 pipelines from Russia to Germany, federal prosecutors say.

The Ukrainian is suspected of being one of the masterminds of the operation, which involved charting a yacht and sailing from the German port of Rostock.

Ukraine has denied involvement in the blasts, which severed a key source of natural gas for Europe.

Although Nord Stream 2 never went into operation, Nord Stream 1’s two pipelines had provided a steady supply 1,200km (745 miles) under the Baltic from the Russian coast to north-eastern Germany.

Shortly before Russia’s invasion, Germany had cancelled its process to approve Nord Stream 2, which was 100% owned by Russian gas giant Gazprom. Months later, Russia shut down Nord Stream 1.

Then, on 26 September 2022, several explosions were recorded close to the Danish island of Bornholm that ruptured three of the four pipelines.

Mystery surrounded the identity of the saboteurs – however last year German reports suggested a team of Ukrainian divers had hired a German yacht and sailed out into the Baltic to attack the pipelines.

German prosecutors issued a warrant for the arrest of a diver named Volodymyr Z last August.

They said the suspect held in Rimini would be brought before an investigating judge after he was extradited from Italy.

The prosecutors said the man was “strongly suspected of jointly causing an explosion and of sabotage undermining the constitution”.

There is no evidence so far linking Ukraine, Russia or any other state to the attacks.