The German government on Monday said that it did not agree with a decision from Copenhagen to reestablish full passport checks between the two countries until January 14. Denmark, fearing a renewed refugee influx, stood by the move in the face of criticism from its southern neighbor, which has borne the brunt of the continent's refugee crisis.

Politicians in Berlin were worried what the decision could mean for the future of the Schengen free-movement zone.

"Freedom of movement is an important principle - one of the biggest achievements [in the European Union] in recent years," German foreign ministry spokesman Martin Schäfer told the press, saying the decision put the Schengen area "in danger."

The solution to the influx of migrants does "not lie on the border between Country A and Country B," said Chancellor Angela Merkel's spokesman, Steffen Seibert, reiterating the administration's determination to find an EU-wide solution to the refugee crisis.

The head of Germany's main police union, Jörg Radek, was even more critical - saying "it cannot be that every nation decides on its own how to proceed, at the expense of security forces who are already being pushed past their limits."

Germany's public railway firm responded that it would not check passports on the country's border with Denmark, leaving that task up to the Danish police.

"Our personnel do not have the necessary knowledge," to conduct such checks, said a spokesman from Deutsche Bahn.

Denmark follows Sweden's lead

The Danish move was itself a knock-on effect of an earlier one from Sweden, with Stockholm deciding to close its bridge and tunnel links to its Nordic neighbor, leaving Denmark worried it would find itself stuck with thousands of migrants who had hoped to travel from Germany to Sweden.

This means that travelers moving between Sweden and Denmark will be obliged to show identification to security agents for the first time since the 1950s, when the countries decided on their own free-movement policy long before the Schengen agreement came into effect.

Swedish Migration Minister Morgan Johansson defended the change, telling reporters the country was "preventing an acute situation where we can no longer welcome asylum seekers properly."

"It's clear the EU is not able to protect its outer borders and other countries are going to be forced to introduce ... border controls," he added.

In his own defense, Danish Prime Minister Lars Lokke Rasmussen cited the Swedish controls, saying "we are simply reacting to a decision made in Sweden... This is not a happy moment at all."

Denmark received 21,000 asylum requests in 2015, while its two neighbors bore the brunt of the crisis, with Germany reporting around 1.1 million applicants and Sweden 163,000.

es/msh (AFP, dpa)