Turkish authorities have intercepted about 1200 migrants trying to reach the Greek island of Lesbos as EU leaders finalised a deal to stem the flow.
About 1200 people, many detained at sea and others in hostels and streets on Turkey's Aegean coast, were being taken to a sports hall in the town of Dikili, a senior local security official told Reuters.
They would be questioned to determine their backgrounds and what action would be taken next.
"I think there are many people running from war to Europe, and I guess it's a [problem]," said Issam Katib, 27, who fled from Damascus and was among those detained.
He reflected a widely held view among the migrants that if they could reach the Greek islands they would then be free to settle in Europe.
"If Turkey gives us the right to choose the country to live in, it is ok, but I think ... in Greece we have the right to choose," he told Reuters, speaking in English.
"We all need [to go] a legal way, maybe not by the sea."
EU deal to settle Syrian migrants in Turkey
Meanwhile, European Union leaders in Brussels clinched a controversial deal with Turkey intended to end the mass influx into Europe of migrants fleeing war and poverty.
Under the pact, from midnight on Sunday (Monday morning NZ time) migrants arriving in Greece would be sent back to Turkey if their asylum claim was rejected.
In return, EU countries agreed to resettle Syrian migrants living in Turkey.
An EU source told BBC up to 72,000 Syrian migrants living in Turkey would be settled in the EU under the agreement.
They added that the mechanism would be abandoned if the numbers returned to Turkey exceeded that figure.
Since January 2015, a million migrants and refugees have entered the EU by boat from Turkey to Greece. More than 132,000 have arrived this year alone.
Tens of thousands are now stuck in Greece as their route north has been blocked.
Greek Interior Minister Panagiotis Kouroublis has compared conditions at the Idomeni camp, on the border with Macedonia, to a Nazi concentration camp.
Doubts remained over whether the deal is legal or workable and aid agencies were highly critical.
Save the Children said it was incredibly disappointed by the initial details of the deal, which it said would only create more uncertainty for many thousands of stranded refugees.
Oxfam said the EU and Turkish leaders had made an agreement that not only failed to respect the spirit of international and EU laws, but may amount to trading human beings for political concessions.
And the British Red Cross said the plan appeared to be about containment, rather than about people's right to protection.
-BBC / Reuters