Turkey has warned Britain and other countries that it will send captured Islamic State suspects and their families back home even if their citizenship has been revoked.

Ankara, which is now in custody of more than 1,000 foreign Islamic State of Iraq and the Levant (Isil) militants, wives and their children after seizing parts of northern Syria from Kurdish forces, said it would not hold them forever.

The UK has so far refused to repatriate any of its nationals from Syria, including three orphans whose parents were killed in an airstrike on Baghuz.

"We will send back those in our hands, but the world has come up with a new method now: revoking their citizenships," Soleyman Soylu, Turkey’s interior minister, said on Monday. "They are saying they should be tried where they have been caught. This is a new form of international law, I guess.

"It is not possible to accept this. We will send back Daesh members in our hands to their own countries whether they revoke their citizenships or not," he said, using the derogatory Arabic acronym for the group.