Eleven people have been found dead and two are missing after a helicopter crashed west of the Norwegian city of Bergen carrying 13, rescuers say.
Eleven of those on board were Norwegian, one was British and one Italian.
Photos from the scene show thick smoke coming from an area of rocky islets.
The helicopter was "totally destroyed", reports said. It was flying from the Gullfaks oil field to Bergen, a centre for the North Sea oil and gas industry.
Oil company Statoil, which said the aircraft was "on assignment" for it, has temporarily grounded all helicopters of the same type, the Eurocopter (EC) 225 Super Puma.
It came down near the small island of Turoey, just west of the village of Solsvik.
Police spokesman Morten Kronen said a major operation, which included firefighters, divers and medical workers, was under way to rescue the two missing people.
Eyewitnesses reported seeing the helicopter's rotor blade come loose and shear off.
"There was an explosion and a very peculiar engine sound, so I looked out the window. I saw the helicopter falling quickly into the sea. Then I saw a big explosion," a local resident told local newspaper Bergensavisen.
Local media said the helicopter dropped 640m in the last 10 seconds before it crashed. Some wreckage was found on the island, and parts of the fuselage are in the sea.
All passengers on the helicopter were employees of Statoil, reports say.
Norway's civil aviation authority said there had been problems with the main gearbox on the EC225 in 2012 and flying restrictions were imposed on it then and in the following year.
The UK's Air Accidents Investigation Branch is sending a team to Norway because it has investigated a number of crashes involving helicopters operating to and from offshore oil and gas fields in recent years.