“This is the first day of a very difficult time for refugee rights. Despite the serious legal gaps and lack of adequate protection in Turkey, the EU is forging ahead with a dangerous deal,” Giorgos Kosmopoulos, head of Amnesty International in Greece, told AP, referring to the operation, which started at dawn and was conducted under heavy security.

“Turkey is not a safe third country for refugees. The EU and Greek authorities know this and have no excuse […] Even if this first group is not refugees, what we are seeing here is symbolic kick off of what might be a very dangerous practice of returns to Turkey,” he added.

Migrants were escorted onto small ferries by officers from the EU border protection agency, Frontex, to nearby ports on the Turkish coast.

“All of the migrants returned are from Pakistan except for two migrants from Syria who returned voluntarily,” Giorgos Kyritsis, a spokesman for a government refugee crisis committee, told state television, adding that there is “no timetable for returns.”

A number of asylum seekers on the islands have reportedly complained of not being given sufficient time and access to the asylum procedure.

Anas al-Bakhr, a Syrian engineer from Homs now stuck on Chios Island, said police marked his arrival date as March 20, although he claims to have arrived the day before.

“They said the computers were broken that day,” the man told AFP.

Senior UN migration official Peter Sutherland has recently warned in an interview on BBC Radio 4’s Today program that “if there is any question of collective deportations without individuals being given the right to claim asylum, that is illegal.”

A total of 50,000 migrants and refugees are stranded in Greece following EU and Balkan border closures, the Ekathimerini Greek daily reported, citing fresh data provided by the government late last month. Only those who arrived after March 20 will be detained for deportation.

Last month EU leaders and Turkey agreed a plan, aimed at opening a "safe and legal" route to the EU for Syrian refugees. The idea is that all new irregular migrants crossing from Turkey into Greek islands will be returned to Turkey; and for every Syrian returned to Turkey from Greek islands, another Syrian will be resettled from Turkey to the EU.

This "temporary link" between resettlement and return is only feasible up to a limit of 72,000, the European Commission noted, however. Commission President Jean-Claude Juncker acknowledged that the European Union and Greece were facing a "Herculean task" to implement the plan.

“I don’t think that this kind of deal can work,” Joaquin Flores of the Independent Journalists Association for Peace told RT. “The direct cause of the refugee crisis has not been resolved. There is still a conflict raging in Syria, which has claimed the lives of half-a-million to a quarter-of-a-million people, depending on reports. Until countries like Turkey and Saudi Arabia can really become a proactive force for curtailing the inflow of terrorist fighters from their countries into Syria, then there will be no end to this conflict – a political solution becomes very difficult.”

@RT_com Turkey forcibly returned hundreds of Syrian refugees to war zone – Amnesty International http://on.rt.com/78t7

In return for re-admitting migrants, Ankara is set to receive more financial aid and a promised visa-free travel in the EU for its citizens. Turkish Interior Minister Efkan Ala said his country is ready to receive 500 refugees on Monday and Greek authorities have provided 400 names, AFP reported.

Up to 4,000 migrants and refugees are being detained on Greek islands since the agreement came into effect March 20. According to Kyritsis, over 130 migrants were deported from Lesbos and more than 60 from the nearby island of Chios.

Scuffles erupted in Chios Island on Sunday night between riot police and local residents objecting to the relocation of migrants, The Toc Greece reported. Locals, protesting the establishment of a temporary migrant accommodation facility at the Tampakika area of the island, worry that it may eventually become a permanent migrant center.

Police sources on Lesbos reportedly said there had been a flurry of last-minute asylum applications on Sunday amongst the 3,300 migrants there.

“We... have over 2,000 people that have stated their wish to seek asylum and we need to see a credible process go ahead with the Greek asylum service for those that wish to express their protection concerns,” Boris Cheshirkov, the UN refugee agency spokesman on Lesbos, told AFP.