CCTV footage shows three British teenagers suspected of planning to join Islamic State (IS) militants in Syria, being arrested at Istanbul airport.
The three teens were arrested on suspicion of preparation of terrorist acts after being detained in Turkey and have since been bailed.
The suspects - two 17-year-old boys and one 19-year-old man, all from northwest London - were arrested on Saturday by officers from the Metropolitan Police's Counter Terrorism Command.
Three males arrested on suspicion of preparation of terrorist acts have been bailed. They were detained as they tried to travel to Syria.Read the full story ›
Three teenagers who were flown back to the UK and arrested on suspicion of preparation of terrorist acts after being detained in Turkey returned to London last night, ITV News understands.
A source said the three male suspects had originally been detained at Istanbul Sabiha Gokcen Airport, Istanbul.
Chairman of the Home Affairs Select Committee Keith Vaz said the number of young people attempting to travel to Syria is "clearly" on a "much larger scale" that authorities initially envisaged.
Speaking today as two teenagers from London remain in custody after being detained in Istanbul for allegedly trying to join IS, he said it was vital for parents and authorities to be vigilant.
I welcome the action that has been taken by the Turkish authorities.
We need to prevent people going in the first place and that is why parents need to be vigilant but we also need cooperation from the Turkish authorities in order to stop them from going further.
We need to be vigilant. Clearly this flight of young people to Turkey in order to go to Syria is on a much larger scale than we envisaged.
Two teenage boys from north-west London, and a third 19-year-old man, who were stopped in Turkey on their way to Syria are being held at a central London police station on suspicion of terrorism offences.
Scotland Yard confirmed the teenagers had returned to the UK today.
A Met police spokesman said: "Officers alerted the Turkish authorities who were able to intercept all three males, preventing travel to Syria.
"On Saturday, March 14 the three males returned to the UK and at approximately 11.10pm were arrested on suspicion of preparation of terrorist acts contrary to section five of the Terrorism Act 2006."
Two 17-year-old boys from north-west London have been detained in Turkey along with a third male aged 19, the Met Police have said.
In a statement the force said: "On Friday 13 March officers from SO15 Counter Terrorism Command were made aware that two 17-year-old boys from north-west London had gone missing and were believed to be travelling to Syria.
"Enquiries revealed that they had travelled with a third male, aged 19 years.
"Officers alerted the Turkish authorities who were able to intercept all three males, preventing travel to Syria. They remain in detention in Turkey. The families have been kept informed of developments."
Three British teenagers have been detained in Istanbul while allegedly planning to cross to Syria to join Islamic state, Turkish officials have said.
The teenagers have not been named and were seized on Friday, sources told Reuters.
Turkish authorities are in touch with their British counterparts to arrange their deportation to Britain this week.