Turkish President Recep Tayyip Erdogan says the EU-Turkey deal on refugees and migrants will only survive if the bloc keeps up its part of the bargain.

"Turkey will not go through with the agreement to take back Syrian migrants from Europe if the European Union does not fulfil its pledges. Personally these kinds of agreements which would pass through my approval won't get permission," he said.

Speaking at a police organisation event, Erdogan listed further details of migrant and refugee transfers that had taken place so far under the deal.

Deportations to Turkey that began on Monday have been delayed due to the increasing number of applications in Greece. A Turkish interior ministry official said there will be no more returns from Greece until Friday.