BRUSSELS/ LEIPZIG - Bitterly-divided European leaders will seek to find a credible response to the continent's worst migration crisis since World War Two at an emergency summit this week.

German chancellor Angela Merkel called on her peers on Sunday to accept joint responsibility.

"Germany is willing to help. But it is not just a German challenge, but one for all of Europe," Merkel told a gathering of trade unionists. "Europe must act together and take on responsibility. Germany can't shoulder this task alone."

Striking a more skeptical tone on migration than in previous weeks, Merkel also warned that Germany could not shelter those who were moving for economic reasons rather than to flee war or persecution.

"We are a big country. We are a strong country. But to make out as if we alone can solve all the social problems of the world would not be realistic," she told a gathering of the Verdi trade union.

European Council President Donald Tusk, who chairs European Union summits, said on Twitter on Sunday following a weekend visit to Jordan and Egypt that the EU needed to help Syrian refugees find a better life closer at home.

That will be one of the topics of discussion for Wednesday's summit in Brussels as hundreds of thousands of refugees and migrants brave the seas and trek across the impoverished Balkan peninsula to reach more affluent countries in northern Europe.

The 28-member bloc has struggled to find a unified response to the crisis, which has tested many of its newer members in the East that are unaccustomed to large-scale immigration. (Reuters)