Hundreds of migrants protested in front of Budapest's eastern railway station on Wednesday, shouting "Freedom, freedom" and demanding to be let onto trains bound for Germany but the station remained closed to them.
More than 2,000 migrants, including families with children, were waiting in the square at the station in sweltering heat.
Asked if Hungary would again let migrants board trains to Germany as it did on Monday, a spokesman for the government said it would observe European Union rules.
"In the territory of the EU, illegal migrants can travel onwards only with valid documents and observing EU rules," he said. "A train ticket does not overwrite EU rules."