The helicopter was transporting people from an offshore oil field
Rescue services say 11 people have been found dead, and two are missing, after a helicopter crashed near the city of Bergen.
A British national was one of 13 people on board the helicopter, according to the Rescue Coordination Centre.
An Italian is also said to have been among the passengers, along with 11 Norwegians.
An British Foreign Office spokesman said: "We are urgently seeking further information from local authorities following reports of a helicopter crash in Bergen, Norway".
The helicopter was carrying workers from an offshore oil field site in the North Sea, and crashed on an island off the coast.
Rescue workers are continuing their search in the hope of finding survivors, a spokesman for Sola rescue centre has said.
Anders Bang Andersen told reporters: "The helicopter has been located and we are doing everything possible to rescue the occupants".
A police spokesman said the helicopter "is totally smashed".
Morten Kronen, of the region's police force, said: "We have not found any survivors. We are still looking. We are searching a large ocean area".
The accident happened around midday local time.
An eyewitness told a Norwegian newspaper that the helicopter's "rotor blades came rushing towards us...then we heard a violent explosion".
Statoil, the energy company that owns the Gullfaks B platform that the helicopter was travelling back from, says it has temporarily grounded all helicopters of the type that crashed.
Norway's Prime Minister Erna Solberg has said on Twitter that she is being continuously briefed on the rescue operations, describing the news as "horrible".
Forferdelige meldinger om helikopterstyrten ved Sotra. Jeg holdes løpende orientert om redningsarbeidet.— Erna Solberg (@erna_solberg) April 29, 2016