The announcement that Russia might charge such a prominent environmental organization as Greenpeace came on a day in which officials from Russia and several other nations, including those with citizens aboard the Arctic Sunrise, gathered for an annual conference on the Arctic held here in the capital of the Yamal-Nenets autonomous region.

Image Credit... The New York Times

The handling of the case cast a shadow on the conference’s themes of health and environmental safety in the Arctic in the face of a changing climate that has opened the seas for longer periods each year. Mr. Putin, who has decreed a new strategy to rebuild Russia’s economic and military power in the Arctic, was scheduled to address the conference on Wednesday.

Greenpeace International sent the ship to the region in August to draw attention to the potential environmental threats caused by a rush to exploit natural resources in a dangerous and fragile region. The oil platform, not far from the island of Novaya Zemlya, or New Land, is the first offshore oil rig in the Arctic. It was completed last year, built to withstand crushing ice floes, and is expected to begin pumping oil next year, though its development has been hampered by complications and delays.

Mr. Markin said in the statement that the activists aboard the ship had carried out an illegal and dangerous act by trying to scale the platform, threatening not only those involved in the offshore confrontation but also the environment that the organization is devoted to protecting.

Maria Favorskaya, a representative for Greenpeace Russia currently in Murmansk, said some of the activists were taken from the Arctic Sunrise to the local office of the Investigative Committee on Tuesday evening. Defense lawyers had gathered there waiting for demonstrators to be delivered from the ship, she said, and expected they would be questioned the same evening.

Kumi Naidoo, the executive director of Greenpeace International, dismissed the charge of piracy, saying that “peaceful activism” is crucial to raise awareness about the impacts of climate change in the Arctic and elsewhere.

“Any charge of piracy against peaceful protests has no merit in international law,” Mr. Naidoo said in a statement. “We will not be intimidated or silenced by these absurd accusations and demand the immediate release of our activists.”