Greenpeace protesters remain attached to the underside of a drilling rig contracted to Cairn Energy PLC (CNE.LN) offshore Greenland , shutting down operations on the rig for safety reasons, the environmental group said in a statement on its website Wednesday.

Four protesters have suspended tents commonly used in rock climbing from the underside of the rig, Stena Don. This is one of two rigs Cairn has operating offshore Greenland, with which it was hoping to drill three or four exploration wells during the summer.

"They've taken enough food with them to last a few days. The hope is that if they can hang on long enough, Cairn will miss the summer drilling window, and have to wait until next year when the sheet ice melts again," Greenpeace said.

"Safety remains our number one priority," said Cairn in a statement. "The actions taken by Greenpeace are primarily a matter for the Greenlandic authorities and Cairn will work with these authorities as they seek to deal with the matter in the most appropriate way."

Greenland 's government condemned the protest as "a very grave and illegal attack on Greenland 's constitutional rights.

"It is highly disturbing that Greenpeace in its chase on media attention with all measures breaks the safety regulations put in place to protect people and the environment," the government said in a statement.

Greenland 's government hopes development of oil and gas resources could spur economic development in the newly independent but geographically isolated country. Greenpeace says drilling in the Arctic is too environmentally risky, particularly in the wake of the oil spill in the Gulf of Mexico .

Greenland 's police and the executive authorities will work to ensure that legal business activities can continue undisturbed, said the country's Premier, Kuupik Kleist.