Some of the 25 Greenpeace activists held at gunpoint by Russian security officers on a ship Thursday might face charges including terrorism, according to a representative of Russia's internal security service, the FSB.
Russian security officers stormed the ship that had been protesting oil rig drilling in Arctic waters on Thursday.
One of the activists onboard the ship told BBC News that about 15 men in balaclavas seized the Arctic Sunrise in the Pechora Sea, an arm of the Barents Sea.
Another unnamed activist told the news organization on Thursday that members of Greenpeace were being held in the galley, while the captain was detained on the bridge of the ship.
A Greenpeaces spokesperson told CNN that the captain of the ship, Pete Willcox, refused the demand made at gunpoint by Russian authorities to sail the Arctic Sunrise toward the port city of Murmansk. It is now being towed.
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"They used violence against some of us, they were hitting people, kicking people down, pushing people," activist Faiza Oulahsen told the Associated Press in a phone call from the vessel.
Some alleged the armed men holding them were members of the FSB.
Liliya Moroz, a representative of the FSB, reportedly told Ekho Moskvy radio Friday that the activists might be charged with terrorism, which under Russian law is defined as any action "violating general safety, frightening the public or influencing government action" that damages property or threatens lives.
The ship's seizure comes just a day after two Greenpeace activists were arrested by the Coast Guard after attempting to board an offshore drilling platform belonging to Gazprom, Russia's state-controlled natural gas company.
The Russian foreign ministry earlier called the environmental group's protest "aggressive and provocative" behavior. It said the activists who tried to board the rig "threatened people's lives and could lead to environmental catastrophe in the Arctic with unpredictable consequences."
Greenpeace, however, has said the Arctic Sunrise was seized in international waters and has demanded Russian President Vladimir Putin order the coast guard to withdraw immediately.