Analysts are pointing out the economic boost refugees and other migrants might bring to Europe
Brussels (AFP) - Europe's borderless Schengen area, which started taking shape 20 years ago, is under new pressure with Germany's reintroduction of temporary border controls to tackle a record influx of refugees.
Under the Schengen rules, a member state like Germany may "exceptionally" reinstate controls at its borders with fellow members like Austria "if there is a serious threat to public policy or internal security," but usually for no more than 30 days.
In such an event, the European Commission, or the executive of the 28-nation European Union, the European Parliament and other Schengen countries must be informed.
The commission said Germany's decision appears to be a "situation covered by the rules" of Schengen, but added its goal is to return to normal open borders as "soon as feasible."
It is not the first time Germany has reimposed passport controls. Berlin partially lifted the Schengen pact with its neighbours ahead a G7 summit held in the Bavarian Alps last June, in a bid to prevent violent protests.
And in 2008, Austria reinstated border controls to tighten security when it was hosting a European football championship with Switzerland.
But Germany's decision on Sunday will likely fuel publicly expressed fears from EU leaders and officials that the Schengen system may not withstand the pressure from the worst refugee crisis in Europe since World War II.
Twenty-two EU countries, plus non-EU Norway, Switzerland, Iceland and Liechtenstein are part of Schengen.
The six EU countries that do not participate are Britain, Ireland, Bulgaria, Romania, Cyprus and Croatia.
Europeans, the commission says, make more than 1.25 billion journeys within the Schengen area every year.
The Schengen area guarantees free movement to more than 400 million EU citizens, as well as to many non-EU nationals, businessmen, tourists or other persons legally present on the EU territory.
The groundwork for borderless travel was laid in 1985 when European countries signed an agreement in the Luxembourg village of Schengen, but implementation took another 10 years.
The first border checks were abolished in 1995 between seven countries: Belgium, France, Germany, Luxembourg, the Netherlands, Portugal and Spain.
The agreement aims to ensure the free movement of people, which officials say is a fundamental right guaranteed by the EU to its citizens.
Any person, whatever his or her nationality, may cross the internal borders without undergoing border checks.
However, national police forces can check travellers as long as their aim is not one of border control.
Member countries on the external borders, such as Hungary on the frontier of non-EU Serbia, take responsibility for imposing controls and issuing uniform Schengen visas.
In the absence of internal border checks, the Schengen Information System (SIS) has been set up to allow police forces in member states to share data and preserve internal security, including fighting organised crime and terrorism.
In the spirit of police cooperation, officers from one Schengen state can pursue suspects in another in serious cases.
Though outside the Schengen area, Britain takes part in SIS as part of law enforcement cooperation.