Croatia on Saturday announced an unprecedented spike in the arrival of migrants on a long, dangerous journey towards western Europe as the continent's worst post-World War II refugee crisis showed no sign of abating.

With many of the people fleeing war and misery flocking towards Germany, a new poll showed Chancellor Angela Merkel's popularity at home has been hit by her policy of openness.

Hungary's hardline Prime Minister Viktor Orban said Friday that Budapest eventually plans to seal its border with Croatia to stop the influx of tens of thousands of migrants bound for northern Europe.

"The influx of migrants is not going to abate... We want to stop people crossing," Orban told reporters in Vienna after a meeting aimed at smoothing over differences with Austrian Chancellor Werner Faymann.

Croatia and Serbia traded ugly barbs Thursday and slammed tit-for-tat border restrictions on each other as Hungary started building yet another razor-wire barrier to keep refugees out, this time with neighboring Slovenia.

The face-off between Zagreb and Belgrade, the worst since they fought a war in the 1990s, came as thousands of migrants continued to stream through the Balkans towards northern Europe, particularly to Germany where Chancellor Angela Merkel warned the EU was a long way from tackling the worst migration crisis it has ever faced.

Hungarian Prime Minister Viktor Orban on Wednesday rejected what he called German Chancellor Angela Merkel's "moral imperialism" in Europe's migrant crisis.

When asked what he expected from Merkel while Europe grapples with an influx of asylum-seekers, the hardline leader grinned: "I have a long list."

European Union leaders, who will gather for an emergency summit on the migration crisis on Wednesday, are expected to give extra funding to Turkey, Jordan, Lebanon and U.N. agencies.

The leaders are hoping that the funding would help stop the flow of refugees to Europe.

The U.N. refugee chief called Tuesday for European states to show solidarity in their response to the continent's worst migration crisis since World War II, ahead of emergency EU talks.

"There is no way to resolve a crisis of this dimension if each country acts alone and based solely on its own interests," United Nations High Commissioner for Refugees Antonio Guterres told Portuguese broadcaster RTP.

German rail operator Deutsche Bahn said Tuesday it would suspend key services to and from Austria and Hungary until October 4, citing border controls introduced to manage a record migrant influx.

The route from Budapest via Salzburg, Austria to the southern German city of Munich has been taken by tens of thousands of refugees in recent weeks.

Hungary's parliament gave Monday the army and police sweeping new powers to keep migrants out as populist Prime Minister Viktor Orban warned that Europe was being "overrun."

"They are overrunning us. They're not just banging on the door, they're breaking the door down on top of us," the right-wing Orban told lawmakers.

Austrian Chancellor Werner Faymann and German Vice Chancellor Sigmar Gabriel on Saturday called for United Nations countries to contribute an extra five billion euros ($5.65 billion) in aid for refugees living in camps in Lebanon and Jordan.

"We have to help countries where the misery is so great that people are going on the road," Gabriel said, in reference to the tens of thousands of migrants -- many of them Syrian refugees -- who have headed to Europe in recent months.

Thousands of migrants sought their way through a chaotic maze of rumor and proliferating border controls in the western Balkans on Saturday.

In the latest chapter in the EU's escalating refugee crisis, Croatia, Hungary and Slovenia tussled over how to cope with a wave of refugees desperate to reach northern Europe.