Thousands of tonnes of oil have spilled into the North Sea during the loading of a tanker off Norway, the oil company StatoilHydro has said.
The oil spill (marked in red) is Norway's second largest ever
The accident occurred at the Statfjord oilfield some 200km (125 miles) away from the west Norwegian city of Bergen.
The spill, estimated at 21,750 barrels (approx 3,000 metric tons), is the country's second largest ever, Norway's oil safety authority said.
The company said the spill was not an immediate threat to the coast.
"It is a significant amount and we are taking it seriously," said Vegar Stokset, a spokesman for StatoilHydro, which operates the Statfjord oilfield.
But he said the spill was "very far from land".
The accident happened in rough weather while the tanker Navion Britannica was loading oil from a storage buoy, the company said.
Mr Stokset said the cause of the spill was not immediately known, but loading had been stopped immediately and production had not been affected.
An aeroplane and a helicopter had been sent to the scene to survey the extent of the discharge, the company said.
The country's Coastal Administration said at least six ships towing equipment for collecting spilled oil had begun work to try to contain the slick.
"StatoilHydro has a good preparedness plan, and a satisfactory system for handling this," said Christian Sletner, head of emergency preparedness for the Coastal Administration.
"The amount of damage could range from completely marginal to relatively large if substantial amounts reach land," he said.
"The chances of it reaching land, at the moment, seem to be relatively small," Mr Sletner said.
Norway's biggest spill was about 12,000 cubic metres (10,700 tons) in 1977.