With the Foreign and Commonwealth Office not changing its travel advice for Turkey, leading holiday firms said normal bookings would apply - effectively meaning that holidaymakers will not be able to change their travel dates or destinations and will not receive refunds if they refuse to go.

Around 14,000 Britons are on holiday in the Marmaris area, where a bomb exploded last night injuring 21 people, including 10 Britons. Five of those injured were on holiday with Thomas Cook.

Yet Thomas Cook and other members of the Federation of Tour Operators today decided to continue their travel plans as normal. "It is a very heavy flying day and those flights have all taken off today as planned," said Graham Lancaster, a spokesman for the FTO, which represents Britain's 14 biggest holiday firms.

"People aren't requesting to come home and in the light of the latest FCO stance, normal booking conditions apply. A disinclination to travel won't be permitted."

He spoke as news was coming through of another explosion in Antalya, 80 miles from Marmaris, which killed two people and injured more than 20.A bigger resort than Marmaris, some 25,000 Britons could be expected to be in the area.

In light of the latest blast, the FTO would consider another conference call among members later today to review it's position, said Lancaster. He added: "Members of the Federation of Tour Operators with customers in Marmaris are keeping clients informed of advice from the UK and local police and government authorities.

"Thomas Cook staff are in close contact and offering help and support to the injured customers. The FTO will continue to liaise with the UK Foreign & Commonwealth Office. No hotels have been affected by the incident."

The latest bombs come as tour operators have been struggling to shift unsold holidays this summer. Thomas Cook's chief executive said recently that many holidays were being sold at below cost earlier this summer, with Turkey among those with unfilled beds.

Turkey has been popular among Britons in recent years. While the number of British visitors to Greece is declining year-on-year, the numbers heading for the budget sandy beaches of Turkey continue to escalate.

In the first quarter of 2006, as many people visited Turkey - 56,000 - as Greece, despite bombs in the resort of Kusadasi last July in which a Briton, 23-year-old Helen Bennett, was killed.

The fact that the Foreign Office advice stops short of advising tourists not to travel to Turkey is in itself not significant - as with Egypt earlier this year, the FCO has recently striven not to advice a blanket travel ban following the economic and political damage that such advices caused to tsunami-affected countries in 2004 and Bali after the 2002 bombing of a nightclub.

Instead, the FCO has couched its advice in the strongest possible way, warning of a "high threat" from terrorism, while recommending not only travel, but also medical insurance before travelling to Turkey.

Turkey has become increasingly attractive as a holiday destination in recent years, with non-stop flights from Stansted to Antalya beginning in May, 2005, the first scheduled flight from the UK direct to the resort.

Four years ago, fewer than one million Britons visited Turkey a figure that rose by five per cent in 2004 - and more than 20 per cent last year to 1.37 million. Meanwhile, the number of Britons visiting Greece slipped from 2.96 million four years ago to 2.43 million last year.

Yet the rise in numbers has been marked by a rise in terrorism incidents - the FCO's website lists 15 separate terrorist attacks since January, 2006. But while the vast majority of incidents are not aimed at tourists, the attacks of the past 24 hours follow another bomb on June 25 in Manavgat, east of Antalya, which killed four people, including three foreign nationals, and injured several more.

In April this year, the Kurdish terrorists behind last year’s Kusadasi bus bombing threatened specifically to target tourists across Turkey this summer. The Kurdistan Freedom Falcons (TAK), responsible for the murders of Helen Bennett and Irish national Tara Whelan last July, warned holidaymakers to avoid Turkey, “or face the consequences”.

“Foreign currency brought in by tourists is the greatest resource of the Turkish state in its attacks against the Kurdish people,” stated the TAK. “We declare that we will target hotels, amusement areas and tourism companies.”

The group made similar threats last summer, distancing themselves from the mainstream separatist groups, such as the Kurdistan Workers Party (PKK) and the People’s Defence Force (HPG), and warning that they would make Turkey “worse than Iraq”.

Other factors are colouring tourists' perceptions of Turkey. The FCO reports a number of sexual assaults in Marmaris, Bodrum, Antalya and Izmir, and warns of "poor" driving standards in Turkey. "Serious traffic incidents are common," it adds, while highlighting issues with rail travel - a train crash on the line between Istanbul and Ankara two years ago killed 38 and injured 80 passengers.

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