The Dutch government has taken Russia to the international maritime court to try and free 30 crew members of the Greenpeace ship Arctic Sunrise.
The group faces piracy charges after being by arrested Russian troops last month during a protest at an oil platform against drilling in the Arctic.
A Dutch government statement said it was asking for the release of the detained crew and the Greenpeace ship before the German-based International Tribunal for the Law of the Sea.
“Because the Netherlands find that the ship’s release and the freeing of the crew is an urgent matter, it has now decided on this step,” it said.
The activists from 18 different countries are being held in the northern Russian city of Murmansk before another court hearing in November.
Piracy carries a 15 year sentence in Russia