Rescue workers stand on the wreckage of a capsized cruise boat in Bahrain
At least 12 Britons and three people with dual British nationality died when a crowded pleasure boat sank off the coast of Bahrain.
They were among 57 people who died when the boat capsized during a party in the Persian Gulf less than half a mile off the coast last night.
Officials fear the British death toll could rise further as some of the 150 passengers remain unaccounted for.
Up to 63 people were rescued from the two-deck Arabic dhow, whose owners said it may have turned over because of overcrowding.
Groups of divers working from small launches were continuing to search the wreckage and surrounding seas today.
Briton Raymond Austin, 50, who works for a concrete company, said he left the boat before it set off on its pleasure trip because he was worried about overcrowding.
He telephoned his daughter Rebecca at their home in Kent to tell her he was well but "shaken up and distraught".
Foreign Secretary Jack Straw said the British Government had offered to assist the authorities in Bahrain.
He said: "We have responded very quickly. The embassy in Bahrain has moved into action and a rapid deployment team has already been sent from London to assist."
Among the dead was an Irishman, as well as four South Africans, two Indian nationals and one person from Pakistan.
Most of the people on board were employees of South African construction company Murray & Roberts and a subcontractor.
They had joined a mix of Bahrainis and other Gulf Arab nationals to celebrate the completion of part of the Bahrain World Trade Centre towers.
The tragedy occurred at about 9.45pm local time (7.45pm BST) shortly after the boat set sail for a two-hour trip from the Marina Club in Manama, Bahrain's capital.
Survivors said the boat capsized without any warning as it returned to the port of Al Muharraq, in the far north east corner of the island state.
Reporter Mazeeha Saeed, of newspaper Al-Watan, said passengers could still be seen in the water, clinging to pieces of wood, when she arrived at the scene.
She said: "Survivors were trying to swim or holding on to a piece of wood or something to save themselves.
"They don't know how it happened because it happened in seconds."
During the rescue operation, US helicopters and divers helped Bahrain coastguards search the water.
Bahrain's coastguard chief, Youssef al-Katem, said an investigation was under way, although it is understood weather conditions in the area were not to blame.
Television footage showed the capsized boat with rescue workers walking on its brown hull and others taking bodies wrapped in white sheets off a small dinghy.
The boat's owner, Isa Al Qobaisi, told Bahrain's Gulf Daily News newspaper that its captain did not want to take the vessel out to sea as it had a capacity for only 100 passengers.
Construction firm Murray & Roberts said that 15 of its staff were safe but 10 others had died in the sinking.
Brian Bruce, the company's chief executive, said managers had travelled from London to the island state to assist staff and families.
He said: "We are deeply shocked by this tragedy. Our sympathy and condolences go out to all those who have been affected."
British Ambassador to Bahrain Robin Lamb was flying back to the Gulf from the UK where he has been attending a leadership conference.
Foreign Office Minister Kim Howells, who is in the Middle East on official business, is also travelling to Bahrain.
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