Eastern European countries resisted on Friday a German push for them to take in more migrants, exposing a deep rift in the EU as video footage stoked concerns about Hungary's treatment of refugees.
Pressing his Czech, Hungarian, Polish and Slovakian counterparts in Prague, Germany's foreign minister warned the influx of hundreds of thousands of migrants could be "the biggest challenge for the EU in its history."
"If we are united in describing the situation as such, we should be united that such a challenge is not manageable for a single country," Frank-Walter Steinmeier said, calling for "European solidarity."
Germany has taken in 450,000 refugees this year, most of them fleeing violence in the Middle East -- particularly Syria -- and Asia. Millions more are stuck in camps in Lebanon, Turkey and Jordan.
But Steinmeier's appeal to agree to new European Commission proposals -- which for Berlin and the UN don't go far enough -- to share around 160,000 migrants among the 28-nation bloc fell on deaf ears among eastern members.
"The solution to this problem cannot be an administrative one, we want to find a solution that is not imposed, but one that will be made jointly," Slovak Foreign Minister Miroslav Lajcak said.
"Migrants don't want to stay in Slovakia."
Separately, Denmark's right-wing government, which this week temporarily suspended trains from Germany carrying migrants bound for Sweden, also said Friday it would not take part.
German Chancellor Angela Merkel on Friday also took flak from her conservative allies in the southern state of Bavaria where most of the migrants arrive.
"We are getting ourselves into an emergency situation we soon won't be able to control," CSU leader Horst Seehofer told Spiegel, adding that it would be hard to "put the cork back in the bottle".
- 500 every hour -
With the bloc continuing to squabble, EU president Donald Tusk said he would call a leaders' summit if a European justice and home affairs ministers' meeting in Brussels on Monday failed to yield a breakthrough.
Facing criticism that his government has been too slow to help, US President Barack Obama pledged to admit at least 10,000 Syrian refugees over a year starting October 1.
EU lawmakers have called for an international conference on migration bringing together the United States, United Nations and Arab countries.
Underscoring the scale of the challenge, a record 7,600 migrants entered Macedonia in just 12 hours overnight, according to a UN official, with more buses on their way from Greece.
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Some 500 more were arriving every hour, according to humanitarian workers and AFP journalists.
Hungarian police said a record 3,601 crossed the border on Thursday having travelled up through Macedonia and Serbia.
From Hungary, the migrants attempt to reach western European countries, principally Germany and Sweden, via Austria, which on Thursday suspended rail services to Hungary.
Germany has placed 4,000 troops on standby for this weekend alone to cope with the influx.
The response of Hungary, which has seen some 175,000 migrants enter this year, has been to lay a razor-wire barrier and for almost 4,000 soldiers to begin erecting a fence four metres (13 feet) high with the help of prisoners from a nearby jail.
Tough new laws taking effect on Tuesday will allow Hungary to jail migrants and mooted legislation will see the army deployed and soldiers and police given wide-ranging new powers.
Further concerns about Hungary were raised Friday by video footage showing migrants inside a holding camp being fed in the words of one volunteer "like animals in a pen", with women and children caught in a scrum.
Hungarian Prime Minister Viktor Orban reiterated Friday that he was merely applying European rules in seeking to register the new arrivals, pinning the blame on fellow EU member Greece for letting migrants leave and travel north.
"Just because Greece is not keeping to the common (Schengen) agreement does not authorise Hungary to give up on the Schengen rules as well," Orban said in Budapest.
Orban has warned against the danger posed to "Christian" Europe by the arrival of Muslim immigrants. He views the new arrivals as economic migrants, not refugees.
- 'Child-kicking racist camera-person' -
Meanwhile, a Hungarian camerawoman who caused global outrage after being caught on film tripping and kicking fleeing refugees, including children, apologised and said she had "panicked".
"I'm not a heartless, child-kicking racist camera-person," said Petra Laszlo, now fired by her employer, a television station close to Jobbik, one of Europe's most extreme far-right parties.
At Presevo, on the Serbian border, hundreds of migrants were Friday waiting to obtain documents allowing them to continue their journey through the Balkan country.
"The night was difficult, we are soaked to the skin," Mustafa Osman, 28, hoping to get to Germany with his father, brother and sister, told AFP.
"The only goal of this exodus is to survive," added Wahid Rashid, 37, trying to dry his passport by holding it above an improvised camp fire.