Hundreds of British fighters who joined Isis are believed to be hiding in Turkey, prompting fears from western intelligence agencies of an increased risk of terror attacks in Europe, The Times has learnt.

When the Isis-held cities of Raqqa and Mosul were retaken this year, thousands of jihadists fled to Turkey, among them at least 300 Britons.

Ciwan Xhalil, a Syrian-Kurdish intelligence officer responsible for dealing with western intelligence agencies over the fate of foreign fighters, said he thought that most Britons had fled Syria.

“The exodus began after Mosul [in Iraq] fell and continued after [Isis] lost Raqqa. We have lots of French in our jails and scores of other nationals but we think most of the British have escaped,” he added.

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