Migrants continued arriving on Greek islands, authorities said Monday in Athens, even after an agreement between the European Union and Turkey seeking to stem the flow of people across the Aegean Sea went into effect midnight Saturday.
In the 24 hours after the deal became effective, 1,662 people crossed from Turkey to Aegean islands, the Greek crisis management authority said.
A day earlier, 875 migrants arrived, while the figure from the three previous days ranged between 239 and 1,498 people.
In Brussels, European Commission spokesman Margaritis Schinas said that the EU is moving "full speed ahead" with the plan agreed with Turkey.
"We are conscious of the difficulties and we are working 24/7 to make sure that everything that needs to be in place for this agreement to be implemented soon is happening," Schinas said.
Greece can immediately proceed with the return to Turkey of irregular migrants - people who do not ask for asylum - under an existing readmission agreement between the two countries.
Asylum seekers who have arrived in Greece from Turkey since Sunday have started having their applications processed. However, they will not be returned to Turkey until Ankara and Athens put in place prerequisite legal changes, Schinas said.
That is expected to take place by March 28, EU sources said on condition of anonymity.
In the meantime, asylum seekers who have arrived since the agreement went into effect will remain on the islands. The aim is for the processing of asylum applications there to take "around a week" before people are returned to Turkey, one source said.
From April 4, the EU plans to start resettling one Syrian asylum seeker directly out of Turkey for every Syrian refugee returned to the country from Greece, up to a maximum of 72,000 people.
How those asylum seekers will be distributed across the EU remains to be finalized.
The European Commission on Monday issued a legislative proposal to lay the ground for the start of the resettlements. Member states will have to grant their approval before it can come into effect.
To ease the pressure on Greece, asylum seekers who arrived before Sunday and have become stranded in the country will start to be relocated to other EU member states, Schinas said.
Anyone who will have arrived after Sunday will not be eligible for this relocation. With the latest arrivals, the number of migrants stranded on Greek soil rose to 50,411, Athens officials said.
Of that, more than 7,000 were on the islands, about 13,000 in the Athens area and the rest in camps in central and northern Greece, including an estimated 13,500 at camp Idomeni on the border with Macedonia.
The European Commission earlier estimated that Greece needs 4,000 employees to handle the influx of migrants and process their status.
In Warsaw, the EU border protection agency FRONTEX said that it has asked member states to provide 1,500 police officers and 50 return and readmission experts to assist Greece in returning migrants to Turkey.
The agency already has 734 staff in the Aegean to help Greece patrol islands that are the main migration gateway.
As the EU-Turkey plan gains hold, concerns are emerging that it may lead migrants to take even greater risks in an attempt to reach Europe and provide fodder for smugglers of people.
"It seems logical that people will look for other, more dangerous routes like they did before," UN refugee agency (UNHCR) spokesman William Spindler told dpa in Geneva. "But right now, nobody has a clue where these new routes will be."