Video said to have been filmed by a Syrian double agent shows UK schoolgirls preparing to cross into Islamic State (Isis)-occupied territory.
Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase, flew from London to Turkey on 17 February to then cross into Syria and are now believed to be living in IS's de facto capital, Raqqa.
Turkey Foreign Minister Mevlut Cavusoglu said they were helped in their journey by a foreign agent. "This person was caught," he told broadcaster A Haber, Reuters reported. "It turned out to be someone who worked in the intelligence services of a country in the coalition."
Turkish newspaper Milliyet reported the individual was working for Canadian intelligence but this has been denied by Ottawa.
Thousands of Westerners have travelled to IS-held territories via Turkey, swelling the terror group ranks over the past two years.
Earlier in March, Scotland Yard's head of counter-terrorism, Mark Rowley, told lawmakers the girls are believed to have financed their escape by stealing jewellery from their families.
Along with the US and EU states, Arabian peninsula nations including Saudi Arabia and Qatar have been involved in the coalition against IS, as well as Australia and Canada.