The search operation launched after a helicopter crashed off the coast of western Norway has been called off and all 13 people on board are presumed dead, rescue officials said.

Boerge Galta, of the Joint Rescue Co-ordination Centre, said "we do not believe anyone can be found alive".

The operation was called off at 5pm local time on Friday after 11 bodies were found.

The cause of the crash was not immediately known.

The Norwegian Civil Aviation Authority said it is immediately banning helicopters of the same type as the one that crashed - Airbus Helicopters EC225LP - from flying in the Scandinavian country or near Norwegian offshore facilities.

The government agency said its decision is "due to the fatal accident", and the ban "would remain in force until revoked".

Joint Rescue Co-ordination Centre spokesman Jon Sjursoe earlier said the helicopter was carrying 11 Norwegians, one Briton and one Italian from the Gullfaks B oil field in the North Sea to Bergen, 120 kilometres (74 miles) away on the Norwegian mainland.

Norwegian broadcaster NRK said 11 people on board were employed by Norwegian oil and gas company Statoil ASA.

Statoil said it had mobilised its emergency response team and had "temporarily grounded all equivalent traffic helicopters".

The company also said it is sending support staff to Bergen to help families of the crash victims.

It said psychologists and other experienced staff will be available at a Bergen hotel, and confirmed that the chartered helicopter was "on assignment for Statoil".

Police spokesman Morten Kronen said the helicopter "totally smashed" as it hit the island of Turoey, near Bergen, and the 11 victims were found on land.

The helicopter's fuselage was found in the water off the island while its rotor system was on land, Mr Sjursoe said.

"It is a very small island and (helicopter) parts are spread partly on land, partly in the sea," he added.

Norwegian media posted photos of huge billows of smoke.

Witness Rebecca Andersen told Norwegian newspaper Verdens Gang that the helicopter's "rotor blades came rushing towards us".

"Then we heard a violent explosion," Ms Andersen was quoted as saying.

Norwegian prime minister Erna Solberg wrote on Twitter about the "horrifying reports" and said she was being kept informed about the rescue work.

British authorities are deploying air accident investigators to Norway to help assist in the inquiry into the crash.

The Air Accidents Investigation Branch is taking part because the UK has investigated several crashes involving helicopters operating to and from offshore oil fields in recent years.

The team will travel to Norway on Saturday.