Turkish authorities have rounded up some 1,300 migrants allegedly bound for Greece, Turkish state media report.
Police detained hundreds of migrants near the western town of Ayvacik, a main crossing point to Greece, according to the Anadolu news agency.
Among those detained were Syrian, Iraqi, Iranian and Afghani migrants as well as some suspected smugglers.
The move comes hours after Turkey and European leaders struck a deal to control the flow of migrants to Europe.
The detainees were sent to a repatriation centre where some could face deportation.
Campaign group Amnesty International said in a statement the move is "illegal as it is unconscionable".
"In the wake of this weekend's EU-Turkey migration talks, it's a stain on the EU's conscience too," said Andrew Gardner, Amnesty's Turkey researcher.

According to the deal with the EU, Turkey will receive €3bn (£2.1bn) and political concessions in return for clamping down on its borders and keeping refugees in the country.
However, concessions will only be made if Turkey meets certain conditions.

More than 720,000 migrants have arrived in Europe on Greek shores so far this year, the International Organization for Migration says, with most arriving from Turkey.
Many are fleeing conflict in Syria, Iraq and Afghanistan, and lived in makeshift camps in Turkey before their journey.
The so-called Islamic State (IS), which has contributed to the instability in Syria and Iraq that many migrants are fleeing, was placed on Turkey's official list of terrorist organisations in 2013.
The state-run Anadolu Agency reported on Monday that Turkey has since detained 2,627 suspected IS members.

BBC