Environmental campaigners claim to have shut down a "dangerous" oil drilling operation by a British energy company in the Arctic.
Greenpeace said four expert climbers in inflatable speedboats had evaded Danish navy commanders to climb up the inside of the Cairn Energy oil rig off Greenland.
The four campaigners are now hanging from the rig 15m above the icy Arctic ocean in tents suspended from ropes, halting its drilling operation, Greenpeace said.
The campaigners, who are protesting against what they claim are the "huge risks" energy companies are taking with the environment by drilling for oil in deep water, say they have enough supplies to occupy the tents for several days.
They claim that if they halt drilling for a short time, Cairn will struggle to meet the deadline to complete exploration before the winter conditions set in, forcing the company to abandon the search for oil off Greenland until next year.
Sim McKenna, from the US, who is one of the climbers, said: "We've got to keep the energy companies out of the Arctic and kick our addiction to oil, that's why we're going to stop this rig from drilling for as long as we can.
"The BP Gulf oil disaster showed us it's time to go beyond oil.
"The drilling rig we're hanging off could spark an Arctic oil rush, one that would pose a huge threat to the climate and put this fragile environment at risk."
The Greenpeace ship, the Esperanza, set sail from London last month with a pledge to target what the environmental group described as one of the 10 most dangerous deep water drilling sites in the world.
Greenpeace said it wanted to highlight problems with oil that went "far beyond" the disaster at BP's Deepwater Horizon rig in the Gulf of Mexico, and pledged to confront the industry head-on over its "reckless" pursuit of oil.