Greenpeace activists have boarded a rig that was due to sail to the Arctic to drill prospects on behalf of oil firm Statoil (STO), the environmental group said on Thursday.
"We have two people on board and 10 on the water to ensure the rig does not leave port. Our activity started at 8am (0700 GMT) this morning," Truls Gulowsen, the head of Greenpeace in Norway, told Reuters.
"We are prepared to stay as long as necessary," he added. The action took place at the Skipavik yard on Norway's west coast, where the drilling unit was being prepared for the upcoming work.
Statoil said last month the rig would drill two exploration wells during the upcoming summer season, with options for a further five wells, adding the West Hercules would provide for a safe and efficient operation.
On Thursday, the oil company said the Greenpeace action would not affect operations.
"There's a contract for upcoming work, but we haven't begun any operations yet in that regard. It's from this summer and onwards," Statoil spokesman Morten Eek said.
Greenpeace and other groups in January lost a lawsuit against the Norwegian government over the continued drilling in the Arctic, arguing that the award of exploration licences violated citizens' right to a clean environment.
The environmental groups have since appealed the verdict.
Reporting by Gwladys Fouche and Camilla Knudsen