The government of the Netherlands has launched legal action against Russia to free 30 Greenpeace activists charged with piracy over a protest against drilling in the Arctic.
Two Dutch people and two New Zealanders, David Haussmann and Jonathan Beauchamp, are among the group of activists being held in custody in the Russian city of Murmansk.
The group was arrested last month over a protest on an Arctic oil rig owned by state-controlled firm Gazprom.
The Netherlands is the first country to take legal action in the case, the BBC reports.
Foreign Minister Frans Timmermans said he was also acting to free the Dutch-flagged Greenpeace ship Arctic Sunrise.
Mr Timmermans said the Netherlands had applied to the UN's Tribunal for the Law of the Sea, which resolves maritime disputes between states. He said his country viewed the ship's detention as unlawful.
Under the rules of the Hamburg-based Tribunal, the Netherlands may apply for the immediate release of the ship and those on board.