Britain has committed 275 million pounds ($420 million) to a planned European Union fund designed to help Turkey accommodate the more than 2 million Syrian refugees it is hosting, the British government said Friday. Prime Minister David Cameron made the commitment during a summit in Malta this week which was aimed at seeking ways to stem a chaotic flow of migrants that threatens Europe's unity and open borders. Spread over the next two years, the commitment will go toward helping Turkey support and improve conditions for refugees, a government spokesperson said. Civil war in neighboring Syria has forced millions to flee across the border, straining resources in countries like Turkey, Lebanon and Jordan. Many of the displaced eventually seek passage to Europe, which is also struggling to cope with the influx of refugees. Britain's pledge forms part of a 3 billion euro fund planned by the EU. Details on how the rest of fund will be structured have yet to be finalized. More than 800,000 migrants and refugees have crossed the Mediterranean to Europe this year, the U.N. said Friday, warning the Greek island of Lesbos especially was overstretched. Since January, 806,000 people have made the perilous sea journey to Europe, with some 660,700 of them arriving in Greece and 142,400 landing in Italy, new figures from the U.N. refugee agency showed. Around 3,460 people have died trying to reach the continent, it said. While the overall number of arrivals is high, the numbers moving through Lesbos are staggering, UNHCR said, describing a continuing chaotic situation on the Greek island which still has the capacity to accommodate only a fraction of the people pouring in by the thousands. "With winter approaching, reception conditions and capacity there remain overstretched and inadequate," spokesman Adrian Edwards told reporters, pointing out that many people, including women, children and even new-born babies were stuck out in the open. More than half of all those arriving in Greece this year have landed on the island. Despite colder weather and worsening conditions at sea, an average of 3,300 people arrived each day in November. Some 16,000 refugees and migrants are currently on the island, which still only has the capacity to accommodate 2,800 people at a time, UNHCR said. "Lesbos is the epicenter of the crisis," the agency's deputy director for Europe, Diane Goodman said, pointing out that "while the influx is manageable at the European level, it is really an extreme challenge for an island alone to cope." UNHCR is currently the only U.N. agency on Lesbos, Goodman said, adding that the agency was working to expand its presence on the island and to quickly increase its staffing there from around 30 now to 40. She urged local authorities to quickly provide the land needed to increase reception capacity to be able to accommodate people properly. Elsewhere, Austria announced it would erect a 3.7-kilometer metal fence along its border with Slovenia, in a new blow to the EU's cherished open-border Schengen accord. The barrier, due to be completed in less than six weeks, will be the first fence between two members of the passport-free zone. Barbed wire would be stored in nearby containers ready to be rolled out along the border if the situation escalated, officials said. Austrian Interior Minister Johanna Mikl-Leitner insisted the "fence conforms to the Schengen accord," adding it was part of temporary measures aimed at "channeling" the human flow. The move came a day after European Union President Donald Tusk warned that Schengen – one of the bloc's most important achievements – was on the brink of collapse as a result of fallout from the migration crisis. Austria's decision is the latest in a series of tough measures taken by countries to tackle the continent's worst refugee crisis since World War II. Germany, which expects up to 1 million arrivals this year, said Friday it would extend temporary border controls implemented in September until mid-February. German Chancellor Angela Merkel defended Friday a decision by her interior minister to reapply European Union rules obliging migrants to request asylum in the first EU country they arrive in, edging away from her open-door welcome to refugees. "I think the decision is right, because we want to get closer to establishing a fair distribution key also in Europe," Merkel said. "We need a fair burden sharing, that's totally clear," she said, adding that the decision to reapply the Dublin rules would be a step that would help to reach that goal in the medium turn. Earlier this week, Sweden also reinstated temporary checks, while Slovenia rolled out razor wire along its frontier with non-Schengen member Croatia. Fellow bloc member Hungary already sealed its southern border with razor wire last month, diverting the influx toward Slovenia, a small nation of 2 million people. Meanwhile, according to a damning new report, by anti-poverty agency Oxam, migrants passing through Bulgaria on their way to Western Europe are subject to "extortion, robbing, physical violence, use of weapons, threats of deportation and police dog attacks." Most said they were abused by police guarding the country's southeastern border with Turkey but some also said they were abused by authorities in Bulgaria's asylum shelters. Interior Minister Rumyana Bachvarova told journalists Friday that she would check the new accusations. "I hope that we can refute these accusations. This is not our policy, I would not have allowed it," Bachvarova said.