The foreign office, which had expressed fears the death toll would rise, said the number of British holidaymakers killed in Thailand had risen to 10, up from eight reported killed earlier.

Another died in Sri Lanka and two others in the Maldives, including one who suffered a heart attack moments before the wave struck, it said.

Foreign Secretary Jack Straw conceded earlier: "We have had a number of deaths of British nationals reported to our embassies and high commissions but they have not yet been confirmed. The numbers will be higher."

The foreign office said the genders, ages and home towns of the British dead could not yet be disclosed, but confirmed that next of kin were being informed.

A spokeswoman said there was no news on the fate of a group of 50 British teachers on holiday in the south of Sri Lanka.

Ian Proud, secretary to the British Ambassador to Thailand, David Fall, said that some of the British casualties had broken bones and serious wounds in addition to score of minor cuts, according to Britain's Press Association.

Foreign Office minister Douglas Alexander told BBC Radio Scotland earlier it was difficult to determine how many Britons had been killed or injured.

The Foreign Office was, he said, relying mainly on information held by foreign governments about the number of Britons who left home for tourist resorts in the affected region over the holiday period.

It was possible, for example, for British citizens to have flown into Thailand from third countries, without the British government knowing it, he said.

He said the immediate priority was to provide information to relatives and families in Britain, and ensure consular and embassy staff could provide help to British citizens involved in the tragedy.

Five British aircraft flew out Sunday to the affected region, he said.

He said the government was looking at ways to bring Britons back home as well as taking the right disaster relief material out to the affected countries.

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