Vienna (AFP) - Austria warned that the European Union's survival was at stake as it pressed Balkan states to reduce the influx of migrants while Greece threatened not to cooperate with future agreements on the crisis if the burden was not fairly shared among member states.
Further undermining the bloc'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, a main entry point for migrants and where thousands of Afghans have been held up at the border with Macedonia, angrily protested at being excluded from the ministerial meeting, underscoring the deep rifts within the EU.
"Greece will no longer agree to any deal if the burdens and responsibilities are not shared proportionally," Prime Minister Alexis Tsipras told the Greek parliament, vowing "We will not allow our country to turn into a warehouse of souls."
A joint statement from the Vienna talks 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 more than 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 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 and for imposing daily limits on the number of migrants who can apply for asylum in Austria or transit to other countries.
But despite sharp criticism, Vienna says that it has no choice, arguing that the EU has failed to get any effective common strategy off the ground.
So far, joint EU efforts to halt the influx, including a deal with Turkey, have failed to bear fruit.
An EU scheme that 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 had no right to "redraw Europe's cultural and religious identity."
- Unilateral -
Countries throughout the western Balkans have begun to impose restrictions, sparked by Austria's much-criticised daily migrant limits.
Macedonia 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," Macedonia's Foreign Minister Nikola Poposki told Germany's Bild daily. "We reacted because of the actions of other countries."
As a result, around 3,000 people were waiting at the Idomeni crossing point between Greece and Macedonia on Wednesday, police said, with the Macedonians 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 a farmers protest.
Yiannis Mouzalas, Greece's minister responsible for migration, said that there were currently some 12,000 migrants stuck in the country, with hundreds more arriving every day.
- 'Response is not closures' -
EU migration commissioner Dimitris Avramopoulos and Dutch Migration Minister Klaas Dijkhoff warned Tuesday of a "humanitarian crisis that might unfold".
Their fears were echoed on Wednesday by Filippo Grandi, the new head of the UN refugee agency UNHCR.
"By closing the borders to people that are asking for help and protection, first of all we do not fulfil our obligations," Grandi said in Athens.
"The response is not closures, it is cooperation... Everybody has to take a share of this burden," he added.
Austrian officials said the conclusions of the talks would be presented to a meeting of EU interior and justice ministers on Thursday in Brussels.