Brussels - An enormous and complex logistical operation involving thousands of EU and other officials was launched on Monday to ship migrants from Greece back to Turkey under a controversial accord between Brussels and Ankara.
In the first wave of deportations, around 200 mostly economic migrants from Pakistan, Bangladesh and other countries were sent back to Turkey aboard chartered Turkish ferries sailing from the Greek islands of Lesbos and Chios.
Under the hard-won deal with Ankara, the European Union accepted that for every refugee from war-ravaged Syria being returned to Turkey from Greek islands, another Syrian refugee will be resettled directly from Turkey to the EU.
Jean-Claude Juncker, the head of the European Commission, the executive of the 28-nation bloc, appointed senior official Maarten Verwey to act as co-ordinator for the operation in Greece.
He oversees about 4 000 staff from Greece, other EU member states, the European Asylum Support Office (EASO) and Frontex, Europe's border control agency.
They comprise border guards, asylum case officers, police officers as well as judges to examine asylum claims and interpreters.
Turkey and Greece have also sent liaison officers to each other's country.
The Commission says 206 escort officers from Frontex were deployed in Greece over the weekend, along with 32 EASO officers. Thirty extra officers are expected by Wednesday.
Frontex received pledges from 21 EU member states to supply 40 readmissions experts and 702 escort officers for the mission. The border agency estimates it will need 50 experts and 1 500 officers.
The Commission estimates it will cost €280m to implement the deal over the next six months.
The EU will help Greece to set up the infrastructure and reception capacity in order to carry out registrations, appeals and large-scale return operations.
The migrants will stay in so-called hotspots, reception centres on the Greek islands where they are identified and registered, according to the Greek authorities.
Those who do not ask for asylum will be sent back to Turkey immediately, while the others will have their requests studied in line with international asylum rules.
The Commission says more than 6 000 migrants have been registered in Greece since March 20, the date the agreement took effect.
Migrants who do not apply for asylum in Greece or whose applications for asylum have been declared "inadmissible or unfounded" will be returned to Turkey.
They can be declared inadmissible and rejected if the country where they will be returned to, such as Turkey, is believed to provide adequate protection.
Under the EU-Turkey accord, Greece was supposed to change its laws to recognise Turkey as a "safe third country".
Greece's parliament on Friday adopted a bill bolstering its migration and asylum services, and activating a 2013 EU directive which says that migrants cannot be sent to a third country where they would face danger or discrimination.
Commission spokesperson Tove Ernst said on Monday: "No-one will be returned to Turkey if they have not received the necessary guarantees of protection from Turkey."
The Greek courts will deal with any appeals from rejected asylum seekers.
People feeling threatened, such as Kurds, will not be sent back.
Asylum requests in Greece, the Commission said, will be dealt with on a case-by-case basis, in line with European and international law as well as the principle of non-refoulement, which bans sending people back to countries where they risk death or persecution.
Migrants sent back to Turkey will either travel by bus through the land border or by boat from the Greek isles, the Commission says. Frontex is operating three ferries, which can each transport several hundred people, and around 10 buses.
The migrants and refugees who arrived before March 20 face expulsion if found to be economic migrants or will be admitted into the EU relocation scheme if they qualify for refugee status.
Under the scheme, 63 000 people are due to be sent from Greece to other EU member states, even if only 581 have been relocated since the scheme was adopted last September.
Some 52 000 migrants are stuck in Greece after Balkan countries closed their borders to stop the biggest influx of migrants since World War II.
Amnesty International has accused Turkey of illegally forcing Syrians to return to their war-torn homeland -- proof that Turkey is not a safe country for refugees, it says.
Turkey rejects the charge, insisting it has not changed its open-door policy for Syrian refugees.