The campaigners were detained on Thursday along with their ship after two Greenpeace activists tried to climb onto a Gazprom offshore platform, in a protest against oil drilling in the Arctic.

The ship was raided by armed Russian men in balaclavas who abseiled down from helicopters. The ship was seized in the Pechora Sea, near the rig.

"It's hard to believe that the so-called activists did not know that the platform is an installation with a high hazard level, and any unauthorised actions on it can lead to an accident, which would not only endanger the people aboard it but also the ecology, which is being protected zealously," Russian legal authorities stated.