(Vatican Radio) Denmark has tightened its border controls with Germany, hours after Sweden imposed similar measures to deter migrants entering from Denmark.
Listen to Matthew French's report:
Denmark has become the latest EU country to impose border restrictions to deal with the flow of illegal immigration in Europe.
The Nordic countries of Finland, Norway, and Sweden have already imposed border restrictions between themselves and other EU countries to restrict the flow of illegal immigrants.
Danish Prime Minister Lars Lökke Rasmussen said the decision was "not a happy moment" but Denmark "must respond" to Sweden's restrictions.
The new controls would not cause a problem for "ordinary" Danes and Germans, Mr Rasmussen said.
However rail commuters from Denmark to Sweden will now have to change trains at Copenhagen Airport and go through checkpoints. The move is expected to cause serious disruption to traffic flows from Denmark.
Sweden's own restriction mean all travellers wanting to cross the Oresund bridge from Denmark will be refused entry without the necessary documents.
An estimated 20,000 commuters daily cross the Oresund bridge, which connects the Swedish cities of Malmo and Lund with the Danish capital, Copenhagen.
The Germany foreign ministry said "Freedom of movement is an important principle, Schengen is very important but it is in danger."
Germany itself introduced border controls on the Austrian frontier in September, and last week Norway, which is not an EU member but belongs to the Schengen area, said refugees coming from other Schengen countries without visas would be turned back.
Meanwhile Finnish authorities are bracing for larger numbers of arrivals over the country's long eastern border with Russia. Most of the arrivals come by air to Murmansk and then by land to the Finnish frontier.
In recent weeks about half of those entering northern Finland have been from Afghanistan, with others from Iraq, Nepal, Bangladesh and various African countries.
As well as beefing up ID checks on all of its border crossings with other EU nations, Finland now prevents travellers from crossing its eastern border by bicycle.