Five British oil workers are among the dead, and another one is missing, after a Swiss-registered plane crashed into the sea off the coast of Libya.

The UK Foreign Office said 13 Britons were aboard the plane, which was transporting oil workers from the Libyan capital Tripoli to an oil refinery. Seven survived and are receiving hospital treatment.

Other nationalities to die in the crash included three Libyans, two Canadians, two Croatians, two Filipinos, and one person each from Tunisia, Pakistan and India. A further 10 Libyans and two Indians survived the accident.

The Shorts SD-360 plane crashed close to the city of Marsa al-Brega, 750 kilometres east of Tripoli on Thursday at around 1135 GMT. Initial reports suggest its engines failed and the pilot was forced to make an emergency landing.

Noel Guckian, deputy head of mission at the British Embassy in Tripoli, spoke to one British crash survivor early on Friday.

"Obviously he's in shock, both from the crash and the fact that a number of his colleagues have died," said Mr Guckian.

Embassy staff were trying to contact the relatives of Britons who died in the accident, he added.

The identity of the dead Britons - all the passengers aboard the plane were men - would not be released until later on Friday, he said.

One of the survivors - oil worker Stewart Bonner, 59, of Limavady, Co Londonderry, Northern Ireland, is being treated in hospital in Libya for broken bones.

But two of his fellow workers died, he told his wife Olive by telephone.

Mrs Bonner said: "He said he had had a lot of X-rays taken and he is very, very upset, obviously and very annoyed about his two mates who he travelled with all the time and worked with.

"They are both dead. "I asked him how did he get out of the plane, but he just said he really didn't want to talk about it, he just said `I'm alive'."

Hit the water and sank

According to the aircraft's owners Avisto, the plane had been leased to Sirte Oil Co in Libya, to transport workers between its headquarters in Marsa el Brega and Tripoli, as well as to some oilfields.

The company said the accident took place at 1135 Libyan time (0935GMT), about two hours earlier than initially thought.

An Aristo statement added: "According to information we have, the aircraft ditched into water on the final approach to Marsa el Brega due to as yet still unknown reasons."

Sirte chairman Ahmed Aoun, said survivors and fellow workers at the company were "shocked" at the accident, and that a land and sea search was continuing for the missing men.

A Swiss official said that shortly before Marsa el-Brega airport, the pilot reported that both engines had stopped working.

"The plane hit the water just off the Libyan coast and sank," Swiss Transportation Ministry spokesman Hugo Schiltenhelm said.

Swiss officials say they are sending an air accident investigator to Libya on Friday. He is flying from the United States, where he has been investigating the 1998 crash of a Swissair plane off the Canadian coast in which 229 people died.

Marsa el-Brega is Libya's main centre for producing petrochemicals and is operated by the National Petrochemicals Company (NAPECTCO).

On Monday, a plane operated by the Swiss regional company Crossair crashed two minutes after take off from Zurich airport, killing all 10 people aboard.

Transport probe

The Department of Transport has also sent two inspectors to Libya to help the local authorities investigate the crash.

A spokesman said the reason for their intervention was twofold - because the aircraft was built in Northern Ireland and because of the British fatalities.

However the spokesman stressed the Libyans were still leading the investigation, although the inspectors would offer every assistance.

The department has also offered facilities at Farnborough for the reading of the aircraft's flight data recorder if required.