Greenpeace accused the Russian security service of piracy, The New York Times reported. Greenpeace Russia said in a tweet its lawyers plan to file court papers seeking the return of the ship, the Arctic Sunrise.
About 15 Russian guards boarded the ship -- which flies a Dutch flag -- Thursday and held about 30 members of the crew in the galley and the captain on the bridge, the BBC reported.
The Federal Security Service said its officers fired a single warning shot while they were boarding the ship, RIA Novosti reported. Otherwise, it said, no weapons were used.
Greenpeace protesters attempted Wednesday to board a Russian oil rig operated by Gazprom subsidiary Gazprom Neft Shelf in the northern Pechora Sea.
The Russian Foreign Ministry said Greenpeace's actions were "aggressive and provocative" and "threatened people's lives and could lead to environmental catastrophe in the arctic with unpredictable consequences."
Greenpeace said it was protesting the Russian oil rig because it alleges modern technology cannot sufficiently clean up a possible oil spill in arctic waters.
The ship was in international waters but within Russia's 200-mile economic exclusion zone.