Ten Britons are among at least 21 people injured after three bomb blasts hit a holiday resort in Turkey.
The main explosion went off on a local minibus as it travelled through the centre of Marmaris close to midnight.
The injured Britons are in hospital, with four in a serious condition. None has life-threatening injuries. Eleven Turks were also injured.
Six Turkish nationals were also injured in Istanbul after a bomb exploded late on Sunday night, local reports said.
Turkish police in Marmaris said only one device apparently detonated properly, on the minibus which was travelling down a busy main street.
BBC correspondent Sarah Rainsford said that the whole area has now been cordoned off by police.
Turkey blasts: Advice
Britons worried about relatives in the area can call the Foreign Office helpline on 020 7008 0000
UK tour operator Thomas Cook said five of its customers are among the injured
Tour operator First Choice says it does not believe any of its customers were caught in the blasts
The other two devices reportedly went off in rubbish bins, but no-one is said to have been injured from these explosions.
A Foreign Office spokeswoman said she believed one explosion occurred by the harbour. It is not yet clear where the third blast happened.
She added consular staff were on the ground in the area.
She said it was likely that the 10 injured were holidaymakers but that British nationals could be living in the area.
Despite the attack, the Foreign Office's travel advice for the thousands of people who visit Turkey each week has remained largely unchanged.
It warns of a high terror threat, but does not dissuade people from travelling to the country.
Tayfun Sentop, a spokesman for the Ahu Hetman hospital, where six of the injured have been taken, said their injuries were "nothing serious".
"They have general body traumas and nothing very serious - they are having treatment as inpatients," he told the BBC.
And Julie Midgley - another Abu Hetman representative - said the six at the hospital, who range from a seven-year-old boy to a 65-year-old woman, had spent a "comfortable" night and "their spirits seem to be good".
The other four Britons were admitted to the Caria hospital.
Suzanne Poyraz, foreign operations manager at the hospital, said they had suffered burns and shrapnel injuries to their legs and lower extremities.
"They are not too badly injured. None of them have got life-threatening injuries, but of course they are terribly shocked and two have got particularly nasty injuries to their legs."
There is no indication, as yet, of who carried out the attacks
She said a couple, a man aged 38 and a woman aged 44 had suffered minor injuries.
A 13-year-old girl and a 73-year-old woman had both undergone surgery.
She said the explosion appeared to come from the bottom or from outside the bus they had all been travelling in.
Robyn Berry told the BBC News website she was travelling on a bus about twenty minutes before one of blasts.
"We got off the bus about 5 metres from where the explosion happened," she said.
ATTACKS IN TURKEY
25 June: 4 killed, 25 injured in southern resort of Antalya
16 April: 31 injured in Bakirkoy district of Istanbul
31 March: 1 killed, 13 injured in Istanbul's Kocamustafapasa district
9 February: 1 killed, 16 injured at internet cafe in Istanbul's Bayrampasa district
18 November: One killed and 11 injured in the Beylikduzu district of Istanbul
She said following the attack "there was chaos and all you could smell was diesel in the air".
Another witness, Danielle Pearson, told Sky News she saw "the remains of what was left".
"There were ambulances and police cars going everywhere.
"It was the usual holidaymakers walking about, everybody out enjoying themselves."
The Federation of Tour Operators (FTO) said its members currently have about 14,000 customers in the resort area.
In a statement, it said: "Our current understanding is that five customers of FTO members - all with Thomas Cook Holidays - have been hospitalised, and Thomas Cook staff are in close contact and offering help and support.
"The FTO will continue to liaise with the UK Foreign and Commonwealth Office. No hotels have been affected by the incident."
A spokesman said holidays were "continuing as normal" and there had not been a rush to cancel holidays or return home.
"Members are not reporting customers wishing to return early in any great numbers - just a handful," he said.
It is currently peak season in Marmaris, which is a popular holiday destination among Britons.
The town is relatively westernised with a large number of bars, restaurants and nightclubs.
There is no indication, as yet, of who carried out the attacks.
Kurdish separatists, Islamic militants and leftist extremists have all carried out attacks in Turkey in the past.
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