Hungary has permitted migrants to use normal train services to move closer to Western Europe through its porous western border, abandoning visa checks that it previously used to prevent them from easily reaching Austria and Germany on public transportation.
The unexpected move came just a day after Hungary, buckling from the pressure of a buildup of thousands of asylum seekers at Budapest's main railway station and on its major highway, shuttled several thousand people to its border with Austria using a fleet of buses.
Austria and Germany, the migrants' predominant destination, agreed to take the busloads as an exceptional measure but emphasized that Hungary must handle the cases of other asylum seekers on its own soil. Hungary likewise billed the bus convoy as a once-only opportunity for migrants to avoid its own asylum system.
Germany has warned other European Union members that they must abide by the bloc's rules on processing asylum seekers.
The country's interior ministry says the so-called Dublin rules, which require asylum requests to be processed in the first EU country they arrive in, are still valid.
It says Germany's decision to allow thousands of migrants in Hungary to travel onward to Germany was an exception and "this does not render the Dublin rules inactive."
The ministry cautioned in a statement Sunday that "big willingness to help, which Germany has shown in the last weeks and months, should not be overstretched."
It added that "Only if this is ensured can Germany continue to do its part to tackle the large number of asylum seekers" coming to Europe.