More than 613,000 migrants and refugees have crossed the Mediterranean to Europe since the beginning of the year and more than 3,100 have died trying, the International Organization for Migration said Friday.
Since January, nearly 473,000 people -- most of them refugees fleeing brutal conflicts in Syria, Iraq and Afghanistan -- have landed in Greece, while more than 137,300 have arrived in Italy, according to the latest figures from the organisation.
The UN refugee agency meanwhile said that although arrivals in Greece had slowed somewhat in October compared to the previous month, there had been a sharp increase in recent days, with as many as 85 boats arriving daily.
"The surge in arrivals could be the result of a temporary improvement in the weather, a rush to beat the onset of winter, and a fear that European borders may soon close," UNHCR spokesman Adrian Edwards told reporters.
He said that throughout the day Wednesday, up to six boats were seen arriving at a time on the island of Lesbos, most of them rubber rafts carrying about 50 people each.
The increase in arrivals has added to an already chaotic situation on the Greek islands, and Edwards said UNHCR staff had been briefly evacuated from a registration site on the island of Lesbos Thursday when violence flared there.
The agency's staff had returned to the centre Friday morning, he said.
As many as 4,000 people meanwhile remained stranded near the landing spot on the north coast of the island, after bus transfers to the reception centre were halted due to the overcrowding there, Edwards said.
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Some of them were now trying to walk the 70 kilometres across the island to its capital Mitilini, he said.
- Risk of hyperthermia -
The UN children's agency spokesman Christophe Boulierac said Friday that between 4,000 and 6,000 people were registered in Greece each day in September, with arrivals peaking on October 9 when 9,000 people came ashore.
Most of those crossing to Greece especially continue their journey up through Europe, sparking the greatest movement of people on the continent since World War II.
More than 132,000 people have for instance been registered in Macedonia since June, UNICEF said.
Thirty-five percent of those registered were women and children, it said, adding that the figures were "likely to be grossly underestimated" since as many as two thirds of those who transit the country are believed to do so without being registered.
Afshan Khan, head of UNICEF's office of emergency programmes, told AFP the agency was deeply worried about the continued movement of people through Europe as winter approaches, pointing out that the children on the move were particularly vulnerable.
"I think there's going to be real risks in the next couple of months of increased hyperthermia," she said.