Refugees could freeze to death as winter approaches, the head of the European Union has said, as leaders warned Europe could soon start "falling apart" if they failed to agree on how to handle the worst refugee crisis since the Second World War.

European leaders met for emergency talks in Brussels to deal with the mass of refugees taking the Balkan route from the eastern Mediterranean to richer EU countries.

With winter approaching and many countries closing their borders, Europe risks adding a humanitarian emergency to the refugee crisis.

Jean-Claude Juncker, president of the European Commission, said a solution was urgently needed to stop refugees freezing to death on Europe's hillsides and riverbanks as winter approaches.

"Every day counts," The Daily Telegraph reported him saying.

"Otherwise we will soon see families in cold rivers in the Balkans perish miserably."

Refugees walk through fields in Romania after crossing from Croatia (AP)

Refugees walk through fields in Romania after crossing from Croatia (AP)

To cope with the flow of refugees, the European commission said that 100,000 places in reception centres should be made available along the route from Greece towards Germany.

The UN refugee agency would help establish half in Greece and half in the countries to the north, the BBC reported.

EU leaders also agreed that the border agency Frontex would step up its activities on the Greek-Macedonian border to ensure people trying to cross there would be registered.

"Europe must show it is a continent of values, a continent of solidarity," said German chancellor Angela Merkel.

"This is a building block, but we need to take many further steps."

Refugees walk through fields in Romania after crossing from Croatia (AP)

Refugees walk through fields in Romania after crossing from Croatia (AP)

Refugees are blocked by Slovenian police in Rogonce after arriving from Croatia (AP)

However, other European leaders had already warned the EU could "start falling apart" if they fail to agree on a viable plan to cope with the refugee crisis.

"If we don't find a solution today, if we don't do everything we can today, then it is the end of the European Union as such," Slovenia's Prime Minister, Miro Cerar, said.

"If we don't deliver concrete action, I believe Europe will start falling apart."

Slovenia, which has a population of two million, has seen more than 60,000 refugees arrive in a matter of days.

Faced with a huge influx of refugees over the summer, Hungary built a fence to stop movement across its border with Serbia.

As a result, refugees switched into Croatia, which also imposed border controls, pushing them into Slovenia.

Refugees settle in Germany Show all 12 1 /12 Refugees settle in Germany Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, plays with his daughter Ranim, who is nearly 3, in the one room they and Mohamed's wife Laloosh call home at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity 2015 Getty Images Refugees settle in Germany Germany A refugee child Amnat Musayeva points to a star with her photo and name that decorates the door to her classroom as teacher Martina Fischer looks on at the local kindergarten Amnat and her siblings attend on October 9, 2015 in Letschin, Germany. The children live with their family at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Kurdish Syrian asylum-applicant Mohamed Ali Hussein (R), 19, and fellow applicant Autur, from Latvia, load benches onto a truckbed while performing community service, for which they receive a small allowance, in Wilhelmsaue village on October 9, 2015 near Letschin, Germany. Mohamed and Autur live at an asylum-applicants' shelter in nearby Vossberg village. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Mohamed Ali Hussein ((L), 19, and his cousin Sinjar Hussein, 34, sweep leaves at a cemetery in Gieshof village, for which they receive a small allowance, near Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, looks among donated clothing in the basement of the asylum-seekers' shelter that is home to Mohamed, his wife Laloosh and their daughter Ranim as residents' laundry dries behind in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany Getty Images Refugees settle in Germany Germany Asya Sugaipova (L), Mohza Mukayeva and Khadra Zhukova prepare food in the communal kitchen at the asylum-seekers' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Efrah Abdullahi Ahmed looks down from the communal kitchen window at her daughter Sumaya, 10, who had just returned from school, at the asylum-seekers' shelter that is their home in Vossberg Getty Images Refugees settle in Germany Germany Asylum-applicants, including Syrians Mohamed Ali Hussein (C-R, in black jacket) and Fadi Almasalmeh (C), return from grocery shopping with other refugees to the asylum-applicants' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat (2nd from L), a refugee from Syria, smokes a cigarette after shopping for groceries with his daughter Ranim, who is nearly 3, and fellow-Syrian refugees Mohamed Ali Hussein (C) and Fadi Almasalmeh (L) at a local supermarket on October 9, 2015 in Letschin, Germany. All of them live at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications, after which they will be allowed to live independently and settle elsewhere in Germany 2015 Getty Images Refugees settle in Germany Germany Kurdish Syrian refugees Leila, 9, carries her sister Avin, 1, in the backyard at the asylum-seekers' shelter that is home to them and their family in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Somali refugees and husband and wife Said Ahmed Gure (R) and Ayaan Gure pose with their infant son Muzammili, who was born in Germany, in the room they share at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity, and are waiting for authorities to process their application for asylum 2015 Getty Images Refugees settle in Germany Germany German Chancellor Angela Merkel pauses for a selfie with a refugee after she visited the AWO Refugium Askanierring shelter for refugees in Berlin Getty Images

Meanwhile, Bulgaria, Romania and Serbia have warned they would not accept being turned into a "buffer zone" for refugees.

They also warned they would close their borders if Austria and Germany stop accepting refugees.

Slovenia said it may have to build its own barrier along its border with Croatia if it receives no help from the EU.

The plan submitted by the European Commissioner aims to slow the passage of refugees through the safe corridor that has formed through central and eastern Europe, The Guardian reports.

Leaders agreed to increase border surveillance, properly register refugees, and stop bus and train transfers to the next border without the consent of the neighbouring country.

More than 650,000 refugees are estimated to have arrived by sea so far this year, the International Organisation for Migration reports.

At least 3,135 are known to have died en route.