Hungary and Croatia traded threats on Saturday as thousands of exhausted migrants poured over their borders, deepening the disarray in Europe over how to handle the tide of people fleeing violence. 

More than 20,000 migrants, many of them refugees from the Syrian war, have trekked into Croatia since Tuesday, when Hungary used a metal fence, tear gas and water cannon on its southern border with Serbia to bar their route into the European Union.

EU leaders, deeply divided, are due to meet on Wednesday in a fresh attempt to agree on how and where to distribute 160,000 refugees among their countries, but the noises from some of the newer members of the bloc were far from friendly.

Hungary, where the right-wing government of Viktor Orban has vowed to defend "Christian Europe" against the mainly Muslim refugees, accused Croatia of "violating Hungary's sovereignty" by sending buses and trains packed with refugees over their joint border. It warned it might block Zagreb's accession to Europe's Schengen zone of passport-free travel.

"Croatia's government has continuously lied in the face of Hungarians, Croatians, of the EU and its citizens," Foreign Minister Peter Szijjarto told a news conference. "What kind of European solidarity is this?"

Austria Migrants

Thousands of people who had been stuck for days in southeastern Europe started arriving in Austria early Saturday after Hungary escorted them to the border. (Christian Bruna/Associated Press)

Croatian Prime Minister Zoran Milanovic said that, unlike Hungary, he would not use "brute force" to keep people out, nor would his government make them stay against their will. The buses and trains would keep running to Hungary, he said.

"We forced them [to accept the migrants], by sending people up there. And we'll keep doing it," he told reporters.

More deaths at sea

Croatia, a country of 4.4 million people forged as an independent state in a 1991-95 war, has suddenly found itself in the way of the largest migration of people westwards since the Second World War. On Friday, Milanovic said the country could not cope, and would simply wave the refugees and migrants on.

Croatia Slovenia Migrants

A child sits with other refugees behind a fence between Croatia and Slovenia at the border station of Obretzje, Slovenia, on Saturday. (Markus Schreiber/Associated Press)

Almost 500,000 people have crossed the Mediterranean to Europe so far this year, increasingly across the water from Turkey to Greece and then up through the impoverished Balkans to the former Yugoslavia, of which Croatia and Slovenia are members of the EU.

Many are rushing to beat rougher seas; on Saturday, a girl believed to be five years old died and 13 other migrants were feared drowned when their boat sank off the island of Lesbos.

A second, exhausted group of around 40 people reached the inundated island in a tiny dinghy following a traumatic journey from Turkey, having paddled through the night with their hands across 10 kilometres of sea when their engine failed.

Hungary Migrants

A man holds his children while crossing a border from Croatia in Beremend, Hungary on Saturday. (Petr David Josek/Associated Press)

Nearly 4,700 migrants were rescued off the coast of Libya on Saturday as they tried to reach Europe but one woman was found dead on board a boat, Italy's coast guard said.

July and August alone brought 150,000 migrants and refugees to Greek shores, about as many as the EU says it is planning to accommodate if it can overcome the opposition of many newer members of the bloc in eastern Europe to the quotas Germany and others in northern and western Europe are calling for.

Destination Germany

The vast majority of refugees want to reach Germany, which has said it expects to receive 800,000 asylum seekers this year.

They kept coming on Saturday, crammed onto bus and train having crossed into Croatia from Serbia and driven north and west towards Hungary and Slovenia. Many spent the night under open skies, and the day searching for shade from a scorching late summer sun.

Croatia Slovenia Migrants

A woman holding a crying baby is pulled out of the crowd of refugees behind a fence that blocks the crossing from Croatia to Slovenia at the border checkpoint in Obretzje, Slovenia, early Saturday. (Markus Schreiber/Associated Press)

Hungarian soldiers are racing to build a fence along the Croatian frontier like the one erected the length of its border with Serbia. The government said on Saturday it had called up some army reservists, mostly to staff garrisons left empty by soldiers deployed to the border.

Hungary said some 8,000 had arrived from Croatia on Friday, with more on their way. Most were sent to reception centres near Hungary's border with Austria, which in turn said about 7,500 had entered since midnight.

Tens of thousands more are expected to head for Austria as the normal routes north into Western Europe have all but disintegrated this week.

Asylum-seekers who had headed into Croatia after being beaten back by tear gas and water cannons on the Hungarian-Serbian border this week found themselves being returned on buses or trains back to Serbia or Hungary after Croatia declared it could not handle 20,700 people who have arrived since Wednesday.

Those who went from Croatia to Slovenia, seeking another way into Austria, faced blocked bridges and determined Slovenian riot police. Police in Slovenia say more than 1,000 migrants have entered the country, but hundreds more are waiting at the border as they let in only limited numbers.

Slovenian Prime Minister Miro Cerar suggested he may have to discuss with neighbouring states the creation of a "corridor" to allow their passage through the tiny country of 2 million people.

European Union enlargement commissioner Johannes Hahn on Saturday proposed giving $1.1 billion US to Turkey to deal with the migrant crisis. He spoke after touring a refugee camp in Gevgelija, on Macedonia's southern border with Greece, where about 5,000 migrants are passing through daily.