European and Balkan leaders have agreed on measures to slow the movement of tens of thousands whose flight from war and poverty has overwhelmed border guards and reception centres and heightened tension among nations along the route to the European Union's heartland.
In a statement to paper over deep divisions about how to handle the crisis, the leaders committed to bolster the borders of Greece as it struggles to cope with the wave of refugees from Syria and beyond that cross over through Turkey.
The leaders decided that reception capacities should be boosted in Greece and along the Balkans migration route to shelter 100,000 more people as winter looms.
They also agreed to expand border operations and make full use of biometric data like fingerprints as they register and screen migrants, before deciding whether to grant them asylum or send them home.
"The immediate imperative is to provide shelter," European Commission President Jean-Claude Juncker said on Sunday after chairing the mini-summit of 11 regional leaders in Brussels.
"It cannot be that in the Europe of 2015 people are left to fend for themselves, sleeping in fields."
Nearly 250,000 people have passed through the Balkans since mid-September.
Croatia said 11,500 people entered its territory on Saturday, the highest tally in a single day since Hungary put up a fence and refugees started moving sideways into Croatia a month ago.
Many are headed northwest to Austria, Germany and Scandinavia where they hope to find a home.
"This is one of the greatest litmus tests that Europe has ever faced," German Chancellor Angela Merkel told reporters after the summit.
"Europe has to demonstrate that it is a continent of values and of solidarity.
"We will need to take further steps in order to get through this."
Slovenian Prime Minister Miro Cerar said his small Alpine nation was being overwhelmed by the refugees - with 60,000 arriving in the last 10 days - and was not receiving enough help from its EU partners.
He warned if no fresh approach is forthcoming "in the next few days and weeks, I do believe that the European Union and Europe as a whole will start to fall apart".
The leaders agreed to rapidly dispatch 400 border guards to Slovenia as a short-term measure.
As they arrived at the hastily organised meeting, some leaders traded blame for the influx with their neighbours, with Greece targeted for the mismanagement of its porous island border.
"We should go down south and defend the borders of Greece if they are not able to do that," said Hungarian Prime Minister Viktor Orban, who claimed he was only attending the meeting as an "observer" because Hungary is no longer on the migrant route since it tightened borders.
But the country that many say is another key source of the flow - Turkey - was not invited, and some leaders said that little could be done without its involvement.