A young migrant boy rests on the floor of a platform after arriving at a railway station in Vienna, Austria September 5, 2015. (Photo:Reuters)
Austrian police said on Saturday around 4,000 refugees had arrived from Hungary by bus at the border since the early morning hours, with many more to come.
"We estimate that around 4,000 have arrived - and I don't think that is the end of it," said Helmut Marban, spokesman for the police in the province of Burgenland, adding some already had continued their journey onwards.
"The numbers could well double, if not more," he told Reuters. A special half-hourly train service was now running to take people from the border to Vienna on top of 20 buses shuttling back and forth between the Austrian capital and the border with Hungary.