Austria says temporary border controls with Hungary will be in effect immediately after midnight.
The country’s interior ministry says the measure could be extended to its borders with Slovenia, Italy and Slovakia if needed.
That reflects the possibility that migrants now streaming into Austria from Hungary could instead try to cross into Austria over those borders in large numbers.
The ministry statement says travellers must carry a passport or EU-recognised identity document if going to those countries now, as well as Switzerland, Germany or the Czech Republic, all EU countries with normally open borders to Austria.
It did not say whether Middle East citizens with travel documents would be allowed to continue.
The ministry says under EU rules the controls, “to maintain public order”, can be extended for up to six months.
Police in Vienna said earlier that the city’s two main train stations are overflowing with migrants.
The EU will hold an extra meeting of justice and interior ministers next week to seek progress on how relocate some 120,000 refugees among its members.
Tuesday’s decision for the September 22 meeting came in the wake of inconclusive meeting of interior ministers on Monday where at least four eastern nations objected to the quota proposals to spread the refugees from Italy, Greece and Hungary across 22 other EU nations.
The EU is also considering a possible summit of all 28 EU leaders next week to assess the migration crisis.