A man has been arrested for allegedly helping three British schoolgirls cross into Syria, Turkey's foreign minister Mevlut Cavusoglu has said.
The man is said to work for the intelligence agency of a country which is part of the coalition against Islamic State (IS) militants.
It is believed Shamima Begum, Amira Abase, both 15, and Kadiza Sultana, 16, left the UK last month to join IS.
It is not known what country the arrested man is from.
Girls' families informed
Mr Cavusoglu said the man was not a national of the country he was working for, nor is he from the US or an EU member state.
A Foreign Office spokesman said: "We are aware that an arrest has been made by the Turkish National Police and that the Metropolitan Police have informed the families of the three girls.
"There has been close cooperation between ourselves and the Turkish authorities, and the foreign secretary is in regular contact with his Turkish counterpart."
Shamima, Amira, and Kadiza, all pupils at Bethnal Green Academy, east London, left their homes on 17 February.
The GCSE students flew to Turkey from Gatwick with Turkish Airlines and are believed to have entered Syria within days, probably to join Islamic State extremists.
CCTV images have shown the teenagers waiting at a bus station in Istanbul on the day they arrived in the country.
They are thought to have been driven to a border crossing point by people smugglers before being met there by IS militants.
Mr Cavusoglu told broadcaster A Haber TV in an interview: "Do you know who was the person who helped these girls?
"This person was caught. It turned out to be someone who worked in the intelligence services of a country in the coalition."
Scotland Yard has previously denied that it took three days to inform Turkey about the missing girls, saying it began working with Turkish authorities the day after they disappeared.
UK police officers have since travelled to Turkey as part of their investigation.
The head of the Met Police apologised to the girls' parents earlier this week after they failed to receive a letter intended for them.
The families had complained after the letter - about a fellow school friend who went to Syria last year - was given to the girls instead of being sent directly to them.
Sir Bernard Hogan-Howe said he was sorry the letter "didn't get through" but told the Home Affairs Select Committee there was nothing more police could have done to prevent the girls leaving for Syria.
The families of the schoolgirls told the committee they would have done more to monitor the girls if they had known one of their friends had already gone to Syria.
About 20 women and girls are thought to have gone to Syria from the UK in the past year, probably to join militant groups.