Greek parliament was Friday set to vote on a bill that prepares its asylum laws for the planned return of thousands of asylum seekers to Turkey, under a deal struck between the European Union and Ankara.
According to the agreement, any migrants who reach the Greek islands from Turkey from March 20 onwards and do not apply for asylum, or fail to qualify, will be returned to Turkey, which is a major transit country for people trying to reach Europe.
The migration deal has drawn sharp criticism from human rights organizations, who have argued that it is unlawful and inhumane.
"In their desperation to seal their borders, EU leaders have wilfully ignored the simplest of facts: Turkey is not a safe country for Syrian refugees and is getting less safe by the day," said Amnesty's John Dalhuisen.
The EU-Turkey deal "can only be implemented with the hardest of hearts and a blithe disregard for international law," he added.
Meanwhile Greek harbour police were Friday preparing to move migrants in Athens' Piraeus port to regulated camps in Greece. Around 5,300 people remain at the port's crowded waiting areas.
Around 700 Afghans are to be brought to official camps in buses on Friday, Greek television network Skai reported.
Migrants are currently sleeping in waiting halls normally used by ferry passengers and in more than 1,000 camping tents put up in the docks. There have been reports of tussles between different ethnic groups as tensions rise.
Many of the migrants are reluctant to relocate to state-run camps, fearing they will be stranded there in poor conditions.