The migrants stepped onto ferries with only a few possessions in their hands, border guards at their sides and Turkey in their immediate futures.
A total of 202 migrants who had crossed illegally into Greece became the first sent back to Turkey as part of a controversial deal with the European Union to stem the continent's migrant crisis.
The migrants who boarded three ferries on the Greek islands of Lesbos and Chios on Monday were transported to the Turkish port of Dikili, the European Union's border agency Frontex said. Authorities said the vast majority of people leaving Lesbos were from Pakistan and those leaving Chios were mostly from Afghanistan.
The plan to deport migrants if they do not either claim or qualify for asylum was agreed upon by EU leaders and Turkey at a summit in Brussels last month. It applies to anyone arriving illegally in Greece from Turkey after March 20, and for every Syrian deported from Europe, a Syrian refugee will be resettled from Turkey to the EU.
The deal received widespread criticism by human rights groups who question the morality and legality of such a plan. There was a small protest by activists in Lesbos as the first boat pulled away.
One group held banners on lifeboats saying, "Ferries for safe passage, not deportation." Others protested at Mytilene port on Lesbos, some with banners aloft saying: "No human being is illegal," and "Wake up Europe."
Aid groups were closely monitoring the situation and said that although the morning removals had been orderly and without incident or aggression, they were concerned that this was the beginning of a process that could see refugees deported.
"We are here to monitor and keep the pressure on in the hope that people are not sent back to where their lives could be put in danger," Amnesty International spokesman Conor Fortune said from Lesbos.
"Everything that we have seen so far flies in the face of European obligations under international refugee law," Fortune said in an interview. "Returns should not be happening unless EU countries can guarantee thorough, individual access to asylum processes and there is a genuine safeguard that Turkey will uphold refugee protections and not forcibly send refugees back to their country of origin."
As part of the EU-Turkey agreement, 32 Syrian refugees were flown to Germany to be resettled Monday and an additional 11 arrived in Finland, the Associated Press reported.
More than 1 million refugees fleeing war or poverty in Syria, Iraq and other Middle Eastern and North African countries have arrived in Europe in the last year.
EU leaders are hopeful that the new measures will act as a deterrent for anyone contemplating the journey across the Aegean Sea into Greece. Recent numbers of migrants are down, but they are still substantial.
About 4,000 migrants have been detained on the Greek islands since the agreement came into effect March 20 and about 400 people a day continue to land on Greek shores.
And as the deportations were taking place Monday, the Greek coast guard said about 79 people had been rescued off the coast the day before.
On Lesbos, the 136 migrants who were removed by ferry on Monday were mostly young Pakistani men. Only one woman was in the group. They were loaded onto buses and driven to the port under the supervision of Frontex guards.
The Greek government's Migration Coordination Center said that none of the group had applied for asylum and there were two Syrians among them who had asked to be returned to Turkey.
A total of 66 people were deported from Chios, including 10 women. They were citizens from Afghanistan, Iran, Pakistan, Congo and one each from India, Somalia and Ivory Coast.
Once arriving in Dikili, western Turkey, they were taken into tents to be registered and given a health check. They were greeted by a small group of people waving a sign that read: "Welcome refugees. Turkey is your home," the AP reported.
Human rights groups argue that Turkey, currently home to about 2.7 million refugees, is not a safe place for migrants and refugees.
Last week, Amnesty said about 30 Afghan asylum seekers were forcibly returned to Kabul from Turkey despite fears they could be attacked by the Taliban.
Turkish Prime Minister Ahmet Davutoglu on Monday urged police to show compassion toward the people who will be arriving on their shores.
Do not "distinguish them from our own citizens," Davutoglu said at a ceremony marking the founding of the Turkish police force 171 years ago.
The United Nations High Commissioner for Refugees, which had initially been critical of the idea of deporting people from Greece, said it was also closely monitoring the process and that it appeared that there had already been a rise in the number of migrants taking an alternative route to Europe by traveling from Libya to Italy.
"We're going to have to see how this plays out over time," UNHCR spokesman Adrian Edwards said in an interview with the BBC. "It's still an uncertain situation as of this morning."
It remained unclear how many deportations would take place in coming days as the Greek authorities struggled to cope with the logistics of processing thousands of asylum requests.
"The number of those repatriated will depend on the processing of data and on cooperation with the Turkish authorities," Migration Coordination Center spokesman Giorgos Kyritsis told state television ERT on Monday.
And although the EU-Turkey agreement is unlikely to deter all migrants from making the life-threatening journey, it has already sparked fear and uncertainty for many of the estimated 50,000 people stranded in Greece.
In the border town of Idomeni, a tent city has sprung up after Macedonia shut its southern border and refused to let people travel north along the Balkan route into wealthier parts of Europe in the north.
Frustrated by the stalemate, some migrants there blocked access to trucks on a national highway Saturday, demanding the borders open. Greek television showed dozens sitting on the road, some with children in arms.
In the Greek port of Piraeus, outside Athens, there was a standoff in recent days between authorities and some of the thousands of people who have set up makeshift camps. The migrants are fearful of moving into alternative accommodations in case they end up being sent far from the city and where living conditions are worse.
When Greek Skai TV asked one woman in the port about going back to Turkey, her response was simple: "No please," she said, waving her hands.
Special correspondents Petrakis reported from Athens and Boyle from London.