The next transfer of migrants to Turkey from Greece has been postponed until later this week at Athens' request.
No further details were given, but the Greek government had admitted earlier the procedure had been slowed by an increase in asylum requests by migrants on the islands of Chios and Lesbos.
Dozens of migrants have staged protests on the Greek island of Lesbos. Thousands are being held in a detention center there under the new EU-Turkey deal.
A German flagged NATO ship has started patrolling the Aegean Sea between Turkey and Greece. The International Organisation for Migration says nearly two-hundred-thousand migrants have reached Europe by sea this year alone. More than 700 people died attempting the trip.
