GWEN IFILL: Europe moved in earnest today to reverse the human flood spilling into the continent. It took the form of deportations from Greece involving the first of what could be thousands of people.

Malcolm Brabant reports on the day's developments.

MALCOLM BRABANT: As dawn broke, the first of more than 200 migrants, mostly Pakistanis and Afghans, were ferried from the Greek islands back to Turkey.

Escorted by officers from the E.U.'s border agency, they were taken to tents for registration and health checks. At the same time, 32 Syrian refugees were flown from Istanbul to Hannover, Germany, to be resettled. The exchange is part of Turkey's deal with the European Union to end more than a year of uncontrolled migration.

MAN: Greece and Turkey are implementing the agreement lawfully and the commission and the agencies are on the ground advising with advice and expertise.

MALCOLM BRABANT: The deal aims to discourage economic migrants and those fleeing conflict from making the perilous sea journey, as well as to close down people-smuggling networks. In return, Turkey receives financial aid and expedited E.U. membership talks.

The Turkish prime minister rejected claims that his nation was not safe for returnees.

AHMET DAVUTOGLU, Prime Minister, Turkey (through interpreter): Today, as we take back Syrian refugees from Europe, my request to our police officers is to treat those who consider Turkey with an embrace of mercy with compassion, and don't distinguish them from our own citizens.

PROTESTERS: E.U., shame on you!

MALCOLM BRABANT: Dozens of protesters gathered at the port in Lesbos to denounce the deportations.

MAN: They are being forcibly returned to Turkey, and Turkey is not a safe country. Turkey has not signed the Geneva Convention in full. Only Syrians are enjoying some kind of protection in Turkey, and all the other migrants and refugees are not protected at all in Turkey.

MALCOLM BRABANT: Human rights groups also claim the operation breaches international refugee conventions.

WOMAN: These are individuals who are fleeing horrific scenes of war and the kind of abuses we know from Aleppo, for example, and we are playing some type of ping-pong with them. These people have a right to asylum, to safety, to protection, and we need to grant it to them.

MALCOLM BRABANT: In all, 50,000 migrants and refugees remain stranded in Greece, unable to travel deeper into Europe. About 4,000 who arrived after March the 20th, the cutoff date, and didn't receive asylum, are being detained for deportation.

But still, they come. In the last 24 hours, more than 300 people made the dangerous voyage to Lesbos.

For the "PBS NewsHour," I'm Malcolm Brabant.