Greenpeace activists who tried to board a Russian offshore oil platform in Arctic waters last week will be charged with piracy.
The 30 environmental activists from 18 countries are on a Greenpeace ship, the Netherlands-registered icebreaker Arctic Sunrise, which was towed into port near the city of Murmansk by the Russian Coast Guard after two activists scaled the Gazprom-owned Prirazlomnaya platform,Russia's first offshore Arctic oil platform.
It was unclear how many of the activists face piracy charges, which carry a potential prison sentence of up to 15 years and a fine of 500,000 roubles (£9,500), but investigators said they would question all those who participated in the protest and detain the "more active" among them.
"When a foreign ship full of electronic equipment intended for unknown purposes and a group of people, declaring themselves to be environmental activists, try to storm a drilling platform there are legitimate doubts about their intentions," the investigators said in a statement.
The Investigative Committee, Russia's federal investigative agency, said the "attack” violated Russian sovereignty and that the activists posed a danger to the work of the oil platform.
The statement continued: "Such activities not only infringe on the sovereignty of a state, but might pose a threat to the environmental security of the whole region."
Greenpeace, which says it aims to draw attention to the threat oil drilling poses to the fragile Arctic ecosystem, has denied allegations of piracy, saying its protest was peaceful, and said Russia's actions violated international law.
A Greenpeace spokesman said: "Peaceful activism is crucial when governments around the world have failed to respond to dire scientific warnings about the consequences of climate change in the Arctic and elsewhere.
"We will not be intimidated or silenced by these absurd accusations and demand the immediate release of our activists."
Greenpeace says scientific evidence shows that an oil spill from Prirazlomnaya would affect more than 3,000 miles of Russia's coastline.
While onshore drilling in Russia is well established significant offshore work is in its infancy despite numerous attempts to make it work and relatively shallow waters. But a decade of high oil prices, scarcity of opportunities elsewhere and a shrinking ice cap has led companies to look to unexploited parts of the Arctic in recent years.