A massive search and rescue operation was underway on Friday afternoon, with emergency workers saying there was “no sign of survivors”.

The helicopter was carrying 11 Norwegians, one Briton and one Italian, the Sola rescue centre told the press.

The Joint Rescue Co-ordination Centre said 11 people are confirmed dead, while two others are missing.

Morten Kronen, a Norwegian police spokesman, said the helicopter was “totally smashed.”

“They are searching in the hope of finding survivors. So far we have not seen any sign of survivors,” a rescue spokesman told Reuters.

The helicopter had been on its way back from Gullfaks B, an oil field operated by Statoil.

“It is a very small island and (helicopter) parts are spread partly on land, partly in the sea,” Jon Sjursoe, a spokesman for Norway’s Joint Rescue Coordination Center, told AFP.

A spokesman for the energy firm wrote on Twitter: “At 12.20 pm Statoil received notification of a helicopter accident. The helicopter was en route from Gullfaks B to Bergen.

“A total of 13 people were on board the helicopter which was a CHC helicopter. Statoil has temp grounded all equivalent traffic helicopter

They also tweeted the number of an emergency hotline for next of kin.

Eyewitnesses told of hearing a large explosion and seeing thick smoke billowing out of the crash site.

“A helicopter came over our heads. Suddenly we heard noises. Then there was a bang, and the helicopter exploded,” a man who gave his name as Langeland told Norwegian news website NRK.

” The whole helicopter just disappeared. We jumped in the car, drove to the pier and were in a boat immediately,” he added.

All emergency services in the area are on “red alert” according to Norwegian news website NRK.

The crash took place on the island of Turoey, near Bergen, according to Mr Kronen.

BP and Statoil have both grounded Super Puma flights in the North Sea and more operators are expected to follow suit.