Directed by Hungarian police officers, migrants make their way through the countryside after they crossed the Hungarian-Croatian border near the village of Zakany in Hungary to continue their trip to north on Friday.

The European Union must quickly establish adequate centers to receive and register asylum seekers in Greece and Italy and then distribute them across the bloc before winter sets in, the United Nations said on Friday.

More than 591,000 people have crossed the Mediterranean by sea this year, including 450,000 to Greece, and this week 85 boats have been arriving daily on the island of Lesbos, the UN High Commissioner for Refugees said.

“We don’t know the full reasons for this surge in arrivals: it 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 a news briefing.

Seven people drowned on Thursday, among them a baby and three children, after their wooden boat and a coast guard vessel crashed during a rescue operation off Lesbos, the Greek coast guard said.

Violence at a crowded registration site on Lesbos on Thursday forced UNHCR staff to evacuate briefly, Edwards said.

He said facilities in Sicily, Greece and other areas “haven’t been adequate to cope with the numbers,” adding: “This is not a crisis that at the moment is being adequately managed.”

The EU has approved a plan to share out 160,000 refugees, mostly Syrians and Eritreans, across its 28 states to tackle the continent’s worst refugee crisis since World War Two. The first 19 Eritrean asylum seekers were transferred from Italy to Sweden a week ago.

The UN Children’s Fund voiced concern about the under-18s who make the perilous journey through Europe without their families. It has set up seven “child-friendly spaces” along the borders of Macedonia, Serbia and Croatia that help 100-200 children a day.

“It’s a respite, because people are moving and they don’t want to stay long,” Afshan Khan, director of UNICEF’s office of Emergency Programmes, said in an interview.

UNICEF estimates that children account for 18 percent of those seeking refuge in Europe. Some 3,900 unaccompanied children were recorded in Macedonia between June and October, while 14,000 unaccompanied minors have sought asylum in Sweden this year, she said.

Khan warned against granting asylum more easily to children of certain nationalities fleeing war than to others.

She added: “If they’re making this hazardous journey, there is something that is driving them and their families that is fundamentally tragic and precarious to make this journey.”

Hungary said on Friday it would close its southern border with Croatia from midnight (2200 GMT), pressing ahead with a unilateral crackdown on the flow of migrants to a Europe still divided over how to handle them.

The move comes a month after Hungary’s right-wing government shut its frontier with Serbia to hundreds of thousands of migrants, many of them refugees from war in Syria, streaming across the Balkan peninsula from conflict and poverty in the Middle East, Africa and Asia.

Hungary has erected a steel fence almost the length of its southern frontier, declaring it has to secure the borders of the European Union from mainly Muslim migrants who it says pose a threat to the prosperity, security and “Christian values” of Europe.

The flow continued unabated on Friday over the border of EU neighbors Croatia and Hungary — between 5,000 and 8,000 per day in recent weeks, picked up by bus on the Hungarian side and driven north to Austria. The vast majority are trying to reach Germany.

With winter approaching and temperatures dropping, they now face being diverted from Croatia into Slovenia, like Hungary a member of Europe’s Schengen zone of passport-free travel, but which has warned it will not tolerate a major influx.

In Zagreb, the Croatian government said it had already agreed a plan with Slovenia to handle the flow of migrants when Hungary sealed the border.

“Croatian Prime Minister Zoran Milanovic is in contact with his Slovenian counterpart Miro Cerar. The Croatian government already has a plan agreed with Slovenia. In the event of Hungary shutting the border, Croatia will start implementing that plan in coordination with Slovenia,” the spokesman said.

“Last station in Croatia!” a Croatian policewoman hollered to up to 2,000 migrants disembarking from a train at the border town of Botovo, tired but determined. “You’ve got a 10-minute walk to another train in Hungary. This way!“

“We are the last refugees,” said Khodarsus, a 35-year-old teacher and father of two young children. “Winter is coming, so we will together arrive in Germany before that, Inshallah.”

The EU has agreed a deal, resisted by some of its members in eastern Europe, to share out 120,000 refugees, only a small proportion of the some 700,000 people expected to hit Europe’s shores this year.

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