Geneva - Greece has witnessed a surge in migrant arrivals in recent days amid fears of worsening weather and closing borders inside Europe, the United Nations and Greek authorities said Tuesday.
The UN refugee agency said it had registered a clear "spike in arrivals" that left some 27,500 packed on Greek islands by Tuesday morning.
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A high-ranking Greek police official told AFP that of 8,000 people who landed in Greece on Monday, 5,000 crowded onto the already overwhelmed island of Lesbos.
The official suggested the hike was "due especially to milder weather, which makes the journey easier, and to the serious concern among refugees concerning the ongoing closure of borders in Europe."
In previous years, the numbers crossing the Mediterranean to Europe have dropped off sharply as winter approaches, but the International Organization for Migration said Tuesday that recent arrivals, averaging around 9,000 a day, far exceeded the summer peaks.
"We are alarmed at how much this is continuing through the cold weather," IOM spokesman Joel Millman told reporters.
Millman suggested that people smugglers were rushing their business out of concern Turkey would soon start cracking down on them, following a recent agreement with the EU.
Greek newspaper Kathimerini quoted police sources hinting Turkey is allowing more departures to put pressure on the EU and improve its leverage in discussions with the bloc, but the high-ranking police source told AFP that was a "hypothesis, which is not held by the authorities."
Nineteen people have died crossing from Turkey to Greece in the past nine days. At least 3,135 people have died making perilous journeys across the Mediterranean this year, according to UNHCR.
The agency's spokeswoman Melissa Fleming warned that the surge in Greek arrivals was putting huge pressure on the country's meagre reception capacities.
She urged the EU to follow through on its commitment to boost "hot spot" reception facilities in Greece and elsewhere to ensure it will be possible to push ahead with an EU scheme to relocate 160,000 asylum seekers within the bloc.
So far, only 19 asylum seekers have been relocated under the plan, from Italy to Sweden and Fleming said she hoped transfers from Greece could soon begin.
One of the biggest challenges, she warned, was to convince refugees to accept transfers to countries other than top picks Germany, Sweden and Austria.