Greenpeace has dismissed suggestions by a Russian agency that its activists engaged in piracy while attempting to board an offshore drilling platform owned by state natural gas company Gazprom.

Greenpeace International's General Counsel Jasper Teulings says the Russian Investigative Committee's announcement that it was formally considering charges of piracy for the group -- which includes two Canadians -- was not valid and "smacks of desperation."

Since the Greenpeace ship was stormed by Russia's Coast Guard in Arctic waters on Thursday, Greenpeace has been unable to reach it by phone.

The activists remain aboard the vessel, which is being towed to the nearest port, Murmansk.

Russian Presidential Chief of Staff Sergei Ivanov told journalists in Stockholm on Saturday that Greenpeace had "acted too radically" and compared its protest to "Somalian-style piracy."

Arctic Campaign Co-ordinator Christy Ferguson has said Paul Ruzycki of Port Colborne, Ont., and a man from Montreal whose name was not released, were arrested when Russian Coast Guard officers boarded their vessel, which Greenpeace says was in international waters.