OSLO (AFP, REUTERS) - Eleven dead bodies have been recovered after a helicopter carrying 13 people crashed off western Norway on Friday (April 29), with the search continuing for the other two, rescue services said.

The helicopter, a Super Puma that crashed en route from a North Sea offshore oil platform, was carrying 11 Norwegians, one Briton and one Italian, the Sola rescue centre said.

It was transporting workers from the oil field when it crashed around midday near the shoreline off the coast of Bergen, Norway's second biggest city.

The crashed helicopter is a Eurocopter model according to the Norwegian Civil Aviation Authority. Eurocopter is made by a subsidiary of planemaker Airbus.

"There have been challenges with this kind of helicopter model in 2012, when errors in the main gear box were identified," the authority said in a statement. "That model received flying restrictions in 2012 and 2013."

Several witnesses had described seeing the aircraft spiral downwards, followed by a powerful explosion, and people were seen in the sea.

"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 daily Bergensavisen.

"Pieces (of the helicopter) flew into the air," she said, adding that she saw a rotor blade detach.

Norway's Prime Minister Erna Solberg said on Twitter she was monitoring reports of the crash.

"Horrible reports of a helicopter crash," Prime Minister tweeted. "I'm being continuously briefed on the rescue operations."

Live footage showed leisure boats rushing toward the scene, where thick black smoke was billowing into the sky.

The accident took place around noon (1000 GMT), and more than an hour later boats could be seen criss-crossing across the water as helicopters hovered overhead. Divers were seen at the site, and ambulances were parked on shore.

On Twitter, police urged people to refrain from using drones in the area.

The helicopter was returning from the Gullfaks B platform, in one of Norway's biggest offshore oil fields, which is operated by state-owned Statoil.

Media reports had initially spoken of up to 17 people on board.