“The defence reiterates that it will not stop until a court has fully examined the international law and human rights implications of the case,” Canestrini said in a statement, arguing his client should be granted immunity for what the lawyer termed a political act.

Described by both Moscow and the West as an act of sabotage, the mysterious explosions in September 2022 largely severed Russian gas transit to Europe, squeezing energy supplies on the continent.

No one has taken responsibility for the blasts and Ukraine has denied any role. Serhii K, described by the defence as a former military officer, was arrested in August near the Italian town of Rimini on a European warrant.

German prosecutors allege he was part of a group of people who planted devices on the pipelines near the Danish island of Bornholm in the Baltic Sea.

He faces charges of collusion to cause an explosion, anti-constitutional sabotage and destruction of important structures.