Greenpeace is suing Russia before the European Court of Human Rights for detaining its members during a protest last year against Arctic drilling, the environmental lobby group said on Monday.

Russian security forces in September detained 30 Greenpeace activists and journalists and seized their Arctic Sunrise ship over the protest at an offshore oil rig owned by state energy giant Gazprom.

The 30, including four Russians, were detained for around two months before being bailed and then benefitting from a Kremlin-backed amnesty.

Greenpeace wants compensation and a declaration that the detention for a peaceful protest was illegal, as it breached the group's right to liberty and to freedom of expression enshrined in the European Convention on Human Rights, to which Russia has acceded.

"We think the Arctic 30 were apprehended and detained in flagrant violation of applicable international and Russian laws," said lawyer Sergey Golubok.

"The reaction of the Russian authorities was completely disproportionate to the peaceful protest that took place," Golubok said in a statement.

The arrested group had faced the risk of lengthy prison sentences before being amnestied, while Russian authorities are still holding the Dutch-flagged Arctic Sunrise.

Greenpeace, which is headquartered in Amsterdam, said it could take over a year for the ECHR to communicate the case to Russia.