Greenpeace says the Russian Coast Guard has threatened to open fire on the Arctic Sunrise.
That's the ship Greenpeace has taken into the North Sea Route.
The activist group is protesting oil exploration in Arctic waters.
Last week, Greenpeace said it had been denied permission to enter Russia's North Sea Route.
The group cried foul and the Arctic Sunrise went ahead anyway.
But this weekend, Russian coast Guard officials reportedly boarded the ship and demanded it turn back.
Greenpeace says the coast guard threatened to use force if necessary.
The Arctic Sunrise is now leaving the area.
Greenpeace says Russia used a heavy-handed response to deal with a peaceful protest.