Two Syrian children laugh as they cuddle a stuffed toy given by wellwishers after they arrived with a train from Budapest's Keleti station at the railway station of the airport in Frankfurt, Germany, early morning September 6, 2015. [Photo/Agencies]

But the logjam broke on Friday when migrants broke out of a teeming camp on Hungary's frontier with Serbia and others escaped a stranded train. Hundreds set off for the Austrian border on foot, chanting "Germany, Germany!"

The scenes were emblematic of a crisis - about 350,000 refugees and migrants have reached the border of the European Union this year - that has left the 28-nation EU groping for solutions amid dysfunctional squabbling over burden-sharing.

A German government spokesman said Chancellor Angela Merkel and Orban had spoken by phone and agreed that the decision to open the borders was a temporary one made for humanitarian reasons.

Austrian Chancellor Werner Faymann told the newspaper Oesterreich he wanted European leaders to hold a summit on migration after an interior ministers' meeting on Sept. 14.