The European Union has welcomed in 74 Syrian refugees from Turkey and sent more than 300 migrants back there under a new agreement between the EU and Ankara.
European Migration Commissioner Dimitris Avramopoulos announced the figures to EU politicians on Tuesday, and noted that "implementing this agreement is a challenge".
Under the deal, which came into force on April 4, migrants arriving in Greece from Turkey after March 20 who do not qualify for international protection will be sent back.
For every Syrian returned, the EU has pledged to accept one Syrian refugee directly from Turkey, where an estimated 2.7 million Syrians are taking refuge from the conflict in their homeland.
The United Nations and rights groups are concerned the deal might infringe on people's rights.
Meanwhile, Turkey's state-run news agency has said two more rockets fired from Syria have landed in a Turkish border town, wounding two people.
The Anadolu Agency said one of the rockets hit a guesthouse in the town of Kilis on Tuesday, while the second landed in an empty field near a bus terminal, wounding two people who were passing by.
Authorities evacuated children from a nearby youth centre which has been turned into a temporary school for Syrian refugees, the report said.
Kilis has been hit by cross-border rocket fire in the past week, prompting Turkish artillery units to retaliate in line with the Turkish military's rules of engagement.
The wider province of Kilis borders areas in Syria that are controlled by the Islamic State group, Syrian Kurdish militia or anti-government Syrian rebels.
An amateur video that aired on Bulgarian TV appears to show three migrants with their hands tied behind their backs and a group of vigilantes ordering them to return to Turkey.
The migrants, carrying backpacks, are lying on the ground restrained with black zip ties.
One of the men surrounding them tells the trio: "No Bulgaria. Go back (to) Turkey," and that they should leave immediately. One of the migrants nods his head to indicate that he understands.
It was not immediately clear when the video was shot, but it appears to be in an area near the Bulgaria-Turkey border.
It aired on multiple Bulgarian TV stations on Monday, after the video first appeared on social media with a comment reading: "Detention of migrants and return to Turkey."