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Giannis Papanikos, Associated Press
A migrant prays at a park where hundreds of migrants are temporarily residing in Athens, Greece, Friday, Aug. 14, 2015. Greece is Europe’s main gateway for refugees and economic migrants, after the alternative route from Libya to Italy became too dangerous. More than 130,000 people have reached the Greek islands this year - a 750 percent increase on 2014.

KOS, Greece — A giant passenger ferry reached the Greek holiday island of Kos Friday, to provide temporary accommodation for crowds of Syrian refugees sleeping rough after crossing clandestinely from Turkey in flimsy boats.

Also Friday, the International Organization for Migration said the number of migrants and asylum-seekers who have crossed the Mediterranean to Europe this year will pass the quarter-million mark by the end of the month — more than half of them arriving in Greece.

The Eleftherios Venizelos ferry, which can take up to 2,500 people, will function from Saturday as a screening center where Syrians can stay as they wait for temporary travel documents to leave the island.

It will replace an old stadium criticized for its lack of basic amenities, where Greek authorities working intensively have screened and issued documents to about 7,000 Syrians since Monday.

Major-General Zacharoula Tsirigoti, head of the Greek police's aliens and border protection branch, said all the Syrians who had arrived on Kos by late Thursday have now been screened. She said the ferry will stay on for about two weeks to cater to new arrivals, whose numbers are expected to drop off as weather conditions deteriorate in the autumn.

The Geneva-based IOM said Friday that financially struggling Greece has reported 134,988 arrivals from Turkey this year, while Italy recorded 93,540 newcomers up to the end of July. Adding in arrivals in Spain and Malta, the group says that 237,000 people have made the crossing in 2015. It is forecasting that the total will top 250,000 by the end of August.

Over the whole of last year, 219,000 made the risky crossing to Europe.

The IOM estimated that at least 2,300 people have died trying to make the crossing this year.

At least two rubber boats carrying men, women and children from Syria safely made the 4-kilometer (2.5-mile) crossing from Turkey early Friday. One landed on a swimming beach in the main town on Kos, where bathers watched as about 40 people in life vests came to shore among the umbrellas and lilos.

The Greek coast guard said it rescued nearly 600 refugees and migrants at sea from Thursday morning to Friday morning, in 21 separate incidents off Kos, and the islands of Rhodes, Chios, Samothraki and Lesbos — where most arrivals are recorded.

Major-General Tsirigoti said about 1,900 Syrians who got their papers are expected to leave Kos Friday on Athens-bound ferries. Another 2,000 left over the past two days, considerably reducing the overall number of people trapped on the island.

While scores of tents remain standing outside the stadium, the situation is much better than at the beginning of the week, when thousands of people were sleeping rough in parks, along the seafront promenade, in the harbor and under the walls of a coastal mediaeval fort.

Dalton Bennett in Kos and Geir Moulson in Berlin contributed to this story.