Turkey says spy detained for helping British girls join IS

"Do you know who helped those girls? He was captured. He was someone working for the intelligence (service) of a country in the coalition," Foreign Minister Mevlut Cavusoglu told the A-Haber channel in an interview published by the official Anatolia news agency.

He said the agent was neither a national of an EU state, nor the US, without specifying further.

"It's not an EU member, it's also not the United States. He is working for the intelligence of a country within the coalition," Cavusoglu said.

He also did not saw where or how the alleged spy had been captured.

Cavusoglu said he had informed his British counterpart Philip Hammond of the development.

"He told me 'just as usual'," said Cavusoglu, without explaining further.

Close friends Kadiza Sultana, 16, and 15-year-olds Shamima Begum and Amira Abase, crossed into Syria after boarding a flight from London to Istanbul on February 17.

They took a bus from Istanbul to the southeastern Turkish city of Sanliurfa close to the Syrian border from where they are believed to have crossed the frontier.

Cavusoglu's comments come amid growing irritation among Turkish officials over repeated criticism from the West that Ankara is not doing enough to stop jihadists and their sympathisers crossing from Turkey into Syria.

Turkey had last month accused Britain of a "reprehensible" delay in informing the Turkish authorities over the departure to its territory of the three teenage girls.

Turkish officials say Ankara has stepped up efforts to stop the flow of jihadists but needs to be given intelligence by Western partners in advance of their arrival in order to stop them.