Hungary's right-wing government shut the main land route for migrants into the European Union on September 15, taking matters into its own hands to halt Europe's influx of refugees.
An emergency effort led by Germany to force EU member states to accept mandatory quotas of refugees collapsed in discord.
Chancellor Angela Merkel appealed for European unity after one of her ministers called for financial penalties against countries that refused to accommodate their share of the migrants, provoking anger in central Europe.
A Czech official described such threats as empty but nonetheless "damaging" while Slovakia said they would bring the "end of the EU".
Under new rules that took effect from midnight, Hungary said anyone seeking asylum on its southern border with Serbia, the EU's external frontier, would automatically be turned back, and anyone trying to sneak through would face jail.
Families with small children sat in fields beneath the new 3.5-metre- (10-foot-) high fence, topped with razor wire, which blocks entry for migrants to the former communist country.
Migrants who tried to apply for asylum in a transit zone of metal containers were swiftly turned away. Macruf Suhufi Abdi Omar, a Somali, told Reuters he had been refused asylum barely an hour after he gave his fingerprints.
Hungarian officials said they had denied 16 asylum claims at the frontier within hours and were processing 32 more. Police had arrested 174 people for trying to sneak across the border.
The great migration has led to the unraveling of one of the 28-member EU's signature achievements, its Schengen system of border-free travel across much of the continent.
