Hungary has reacted angrily to comments made by the Austrian premier likening the the country's treatment of refugees and migrants to Nazi deportations during the Holocaust.

Photo: AFP / ATTILA KISBENEDEK

The Hungarian Foreign Minister, Peter Szijjarto, said the coments were unworthy of a 21st century leader.

Earlier, Chancellor Werner Faymann said putting refugees on trains and sending them somewhere different to where they expected, was reminiscent of the darkest days of Europe's history.

German vice-chancellor Sigmar Gabriel was also critical of the Hungarian prime minister, Victor Orban, saying he must comply with European law.

Mr Orban has said EU leaders are "in a dream world" about the dangers posed by the influx of people seeking asylum.

More than 170,000 migrants have crossed into Hungary from Serbia so far this year, trying to get to Austria and Germany.

From Wednesday, Hungary will treat what it describes as illegal arrivals as criminals and arrest them.

Refugees and migrants continue to stream into Germany, favoured for its generous welfare system and relatively liberal asylum laws.

Over 9000 people arrived at Munich's main train station last night and the authorities said they would struggle to cope.

Photo: AFP

Meanwhile, tens of thousands of Europeans rallied in solidarity with the plight of migrants seeking refuge on the continent.

The largest crowds were seen in Copenhagen and in London, where protesters voiced their anger at what they regard as the British government's woeful response to the crisis.

In London, thousands of people marched brandishing placards reading "Open the Borders".

In Copenhagen some 30,000 took to the streets, while other demonstrations were planned in Germany, Spain, France and elsewhere.

But highlighting the way in which the arrival of hundreds of thousands of migrants and refugees is dividing the EU, several counter-demonstrations were also scheduled in eastern European countries.

In Poland, nearly 5000 opponents chanted anti-Islamic slogans in Warsaw, while a counter-demonstration drew around 1000 people welcoming migrants into the country.

UN calls for international help

The United Nations estimates one million more people will be displaced within Syria by the end of the year if the civil war there continues.

The UN's humanitarian coordinator, Yacoub El Hillo, is calling for more international help for Syrians caught up in the fighting between the government, disparate rebel groups, and Islamic State.