Austria warned Wednesday that the EU's future was at stake as it pressed Balkan states, in the absence of an effective common response by the bloc, to reduce the influx of migrants despite fears of a humanitarian crisis.
Further undermining the European Union's hopes to get a grip on the situation, Hungary meanwhile announced a referendum on Brussels' troubled scheme to share out migrants among the 28-nation group via mandatory quotas.
"We have to reduce the influx now. This is a question of survival for the EU," Austrian Interior Minister Johanna Mikl-Leitner said after talks in Vienna with countries on the well-trodden west Balkans route north from Greece.
Greece, where thousands of Afghans have been held up at the border with Former Yugoslav Republic of Macedonia (FYROM), angrily protested at being excluded from the ministerial meeting, underscoring the deep rifts within the EU.
A joint statement from the participants said that after hundreds of thousands of people trekked through the Balkans last year, many ending up in Germany, Sweden and also Austria, the inflow must be "massively reduced".
The talks come after figures showed over 110,000 people arriving in Greece and Italy so far this year alone -- 413 perishing in the attempt - following more than one million arrivals in 2015.
Amnesty International hit out Wednesday at Europe's "shameful" response, saying most EU countries had "simply decided that the protection of their borders is more important than the protection of the rights of refugees".
Vienna has come under fire for organising Wednesday's talks, not least from Greece, and for imposing last week daily limits on the number of migrants who can apply for asylum in Austria or transit to other countries.
But despite sharp criticism also from Germany, Vienna says that it has no choice because the EU has failed to get off the ground any effective common strategy.
"I am optimistic that we can reach a joint EU response. The question is when," Mikl-Leitner told a news conference. "We want to generate pressure so that the EU can reach a solution."
So far joint EU efforts to halt the influx, including a deal with Turkey - the subject of a March 7 special summit - to stem the mass exodus of migrants across the sea to Greece, have failed to bear fruit.
An EU scheme agreed in September to relocate 160,000 people among EU nations under mandatory quotas, has seen just 598 relocated so far, with former communist members of the bloc opposing the plan and filing legal challenges.
Hungarian Premier Viktor Orban, announcing on Wednesday plans for the so-far undated referendum, said that Brussels has no right to "redraw Europe's cultural and religious identity."
As a result of the lack of the EU's failures, countries throughout the western Balkans have begun unilaterally to impose restrictions, sparked by Austria's much-criticised daily migrant limits.
FYROM has closed its frontier to Afghans and introduced more stringent document checks for Syrians and Iraqis seeking to travel to northern and western Europe.
"We did not take a unilateral decision," FYROM's Foreign Minister Nikola Poposki told Germany's Bild daily in an interview published Wednesday. "We reacted because of the actions of other countries."
As a result on Wednesday, around 3,000 people were waiting at the Idomeni crossing point between Greece and FYROM, police said, with FYROM allowing 860 people through overnight.
Greek authorities were attempting to take hundreds by bus back to Athens, but were being hindered by a blockade of motorways by farmers protesting for weeks about tax and pension reforms.
Yiannis Mouzalas, Greece's minister responsable for migration, said that there were currently some 12,000 migrants stuck in the country, with hundreds more arriving every day.
EU migration commissioner Dimitris Avramopoulos and Dutch Migration Minister Klaas Dijkhoff said Tuesday they were "concerned" by the developments and by the "humanitarian crisis that might unfold".
Their fears were echoed by Filippo Grandi, the new head of the UN refugee agency UNHCR on a visit Tuesday to the Greek island of Lesvos, where many of the migrants who survive the perilous sea crossing from Turkey come ashore.
"I am very worried about the news that we are getting about increasing closures of European borders along the Balkans route because that will create further chaos and confusion," Grandi said.
Austrian officials said that the conclusions of the talks would be presented to a meeting of EU interior and justice ministers on Thursday in Brussels.