Thousands of migrants walked unhindered across the border into Austria from Hungary on Monday, where the frontier was kept open despite Germany's sudden reintroduction of checks.
Police said emergency accommodation was filling up for migrants, some of whom have been housed in tents and sleeping in car parks while Vienna decides whether to keep its border open or follow Berlin's lead and act to curb arrivals.
Germany and Austria acted in unison more than a week ago to lift restrictions on migrants entering their territory as tens of thousands of people, many of them fleeing Syria's civil war, trekked up through the western Balkans towards Germany.
But Berlin's decision on Sunday to reverse course appeared to catch the Austrian government by surprise. At a hastily convened news conference on Sunday night, the Chancellor and Vice Chancellor gave no clear indication as to whether Austria would reintroduce checks.
Under the EU's two decade-old Schengen system, border controls have been abolished between 26 European countries. But the rules still forbid undocumented migrants from crossing the bloc's unguarded internal frontiers, creating chaotic scenes in recent weeks as governments tried to cope with unprecedented arrivals.
Nearly all migrants reach the EU's southern and eastern edges and then proceed over land for the richer and more welcoming countries further north. In August, Germany suspended EU policy to allow Syrians to apply for asylum there regardless of where they first entered the bloc, creating more incentive for refugees cross the EU to reach it.
An Austrian police spokesman said that by mid-morning, 6,000 to 7,000 people had arrived since midnight, after 14,000 on Sunday, the highest daily figure yet.
"The accommodation centres in Nickelsdorf, Parndorf, and in the near surroundings are all full," he said, referring to the area near the border crossing where almost all migrants have arrived from Hungary recently.
"At the moment, no buses are running," he said. "The only buses that are running are taking people to the station until a special train leaves, but otherwise we have no accommodation at the moment."
A nearby motorway was closed in both directions because of the number of expected migrants, road operator ASFINAG said in a statement. The rail link to Hungary has been closed since Thursday because Austria has struggled to cope with the influx.
A train service was running to Vienna, and buses had taken people to other parts of the country overnight, the police spokesman said, adding that the number of people entering south of the main crossing point was growing.
At Heiligenkreuz, where until recently only dozens of migrants had crossed each day, arrivals had reached 1,000 to 2,000 on Sunday, in addition to those counted at the main crossing, he said. More were expected on Monday.
Whether Austria would follow Germany's lead in reintroducing border controls remained unclear.
The coalition government appeared to be divided between the Social Democrats, including Chancellor Werner Faymann, who adopted a wait-and-see approach, and the members of the conservative Austrian People's Party, led by Vice Chancellor Reinhold Mitterlehner, who said checks were needed quickly.
