By Bojan Kavcic
The EU has called a mini summit with Balkan countries on the migrant crisis, as Slovenia became the latest state to buckle under a surge of refugees desperate to reach northern Europe before winter.
The leaders of Austria, Bulgaria, Croatia, Germany, Greece, Hungary, Romania and Slovenia will meet in Brussels on Sunday (local time) with their counterparts from non-EU states Macedonia and Serbia, the office of European Commission president Jean-Claude Juncker said on Wednesday.
"In view of the unfolding emergency in the countries along the western Balkans migratory route, there is a need for much greater co-operation, more extensive consultation and immediate operational action," a statement said.
The continent has been struggling to find a unified response on how to tackle its biggest migration crisis since 1945.
More than 600,000 migrants and refugees, mainly fleeing violence in Syria, Iraq and Afghanistan, have braved the dangerous journey to Europe so far this year, the UN said.
Of these, more than 3000 have drowned or gone missing as they set off from Turkey in inflatable boats seeking to reach Greece, the starting point for the migrants' long trek north.
With the crisis showing no sign of abating, France's Interior Minister Bernard Cazeneuve reinforced security in the port city of Calais from where migrants and refugees try to cross to Britain.
He also announced that women and children would be given heated tents, as arrivals in a makeshift camp face a dip in temperature.
The goal for many migrants is the EU's biggest economy Germany, which expects to receive up to a million asylum requests this year.
Chancellor Angela Merkel on Wednesday said the influx of asylum seekers into Germany was part of the fallout from globalisation which, she noted, had served Germany well on exports and jobs.
The Turkish government, meanwhile, warned it was bracing for a mass exodus from neighbouring Syria amid escalating violence there.
Since Saturday, when Hungary sealed off its border with Croatia, more than 24,450 migrants have arrived in Slovenia, a nation of two million people.
In response to the crisis, the parliament has voted to grant greater powers to the army and allow soldiers to join border police in patrolling the 670-kilometre frontier with Croatia.
Ljubjana also voiced sharp criticism over Zagreb's decision to open its borders on Monday night, letting thousands of people into Slovenia.
Around 11,000 people were stuck in Slovenian registration centres on Wednesday, waiting to continue their journey to Austria.
Further south, long lines also formed near Croatia's border with Slovenia.
There was a moment of panic near another Croatian border crossing when 27 tents suddenly caught fire at the Brezice refugee camp.
Firefighters managed to quickly extinguish the blaze, which sent black smoke billowing into the sky.
Forced to spend hours in freezing temperatures and rain, people often resort to lighting makeshift fires to warm themselves.
EU conservative parties meeting in Madrid on Wednesday called for the bloc's external borders to be strengthened, warning the flow of migrants could "destabilise" the region.
"We cannot accept millions and millions more people which we would not know how to manage," said Joseph Daul, chairman of the centre-right European People's Party which unites conservative parties from across the EU.
But Juncker said Europe had a duty to help the migrants.
"I don't often cry but when I see, night after night, this long procession of refugees which reminds me of images from the end of World War Two ... it almost makes me cry," he said on Wednesday.