Greenpeace says its activists have stormed a floating oil rig in Russia's Pechora Sea to protest against oil drilling in the Arctic.

Greenpeace said in a statement that six activists boarded the Prirazlomnaya platform early this morning and remain on the rig.

They set off in inflatable speedboats from their ship and scaled the platform with mooring lines.

The platform is owned and operated by a subsidiary of Russian energy giant Gazprom, which is pioneering Russia's oil drilling in the Arctic.

Russian and international environmentalists have warned that drilling in the Russian Arctic could have disastrous consequences because of a lack of technology and infrastructure to deal with a possible spill in a remote region with massive icebergs and heavy storms.

The activists, which include Greenpeace's chief Kumi Naidoo, did not face much resistance from oil workers and managed to put a banner on the rig, which read: "Don't kill the Arctic."

"We're here peacefully and we will continue to draw the attention of Russian people and people around the world to what's happening there," Mr Naidoo said. "It's bad for Russia, it's bad for the planet."

The state-owned company Prirazlomnaya installed the drilling platform in the Arctic last year and is preparing to drill the first well.

Mr Naidoo said that his teams were suspended from the platform's mooring lines. He added many of the platform's employees "have been very friendly, engaging in conversations with us, asking where we come from and offering us soup".

Mr Naidoo said the activists have been told by one of the platform employees that a coast guard helicopter is on its way to detain them.

The platform is about 1,000km from the nearest port - Murmansk, a city on the extreme north-western edge of the Russian mainland.

Gazprom would not comment on Greenpeace action, but said it would issue a statement later.

Greenpeace said that its activists have supplies to last "for an extended stay".

An AP investigation last year found that at least 1% of Russia's annual oil production, or 5 million tons, is spilled every year.

A report by Greenpeace and World Wildlife Fund, issued last week, said that a spill from Prirazlomnaya could contaminate protected areas and nature reserves on the shore and islands within 20 hours, while emergency teams would take at least three days to reach the area.