Three British teenagers suspected of attempting to join Islamic State have been released on bail.
A man aged 19 and two 17-year-old boys, all from northwest London, were arrested on Saturday night on suspicion of preparing terrorist acts after returning to the UK, police said.
They were apprehended at Sabiha Gokcen airport in the Turkish city of Istanbul.
It is believed they travelled from England to Spain before flying on to the country.
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.
“They have been bailed to return to a central London police station pending further enquiries.”
The trio have not been named, but Sky sources in Turkey say the initials of the men are GH, MNG, and MA.
The Met police said counter-terrorism officers were alerted on Friday that two 17-year-olds from northwest London had gone missing and were believed to be travelling to Syria. Inquiries revealed they had gone with a third male, aged 19.
Reports suggested their families told police they were missing and believed to be travelling to Syria.
Scotland Yard declined to say exactly how long in total they had been away from home.
The developments point to a new level of cooperation between the UK and Turkish police forces, which has faced criticism after three British schoolgirls travelled to Syria to join IS.
Kadiza Sultana, 16, Shamima Begum, 15, and Amira Abase, 15, flew to Istanbul on 17 February and are feared to have continued to Syria to become so-called “jihadi brides”.
The girls’ families issued a statement on Sunday, saying they were feeling their absence “more acutely on Mothers Day” and were praying for their “immediate safe return”.
The statement said they felt let down by the girls’ school, the local council and the police, and accused them of failing to “act appropriately and pass on vital information”.
“Had we been made aware of circumstances sooner, we ourselves could have taken measures to stop the girls from leaving the UK,” said the families.
“Looking to the future, we hope to work with the relevant authorities to rectify the situation, and we will continue to do everything we possibly can to ensure our girls are brought back to us safely.”
The National Police Counter Terrorism Network has launched an advertising campaign highlighting how the strong relationship between a mother and a daughter can be used to open discussions such as travelling to Syria and what the young woman is viewing online.
The girls, who all attended Bethnal Green Academy in east London, are believed to be staying in a house in the IS militants’ stronghold Raqqa.
Speaking after the arrests of the three males, Keith Vaz, chairman of the Home Affairs Select Committee, said: “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.”