Germany has reintroduced border checks scrapped decades ago as part of its membership of the European Union, in a move aimed at reducing cross-border crime and the flow of immigrants into the country.

The checks — reintroduced in the west and north of the country on Monday along borders with Belgium, France, Denmark, Luxembourg and the Netherlands — increased tension between Germany and its neighbors and seemed to signal the end of the EU ideal of borderless, visa-free travel.

The country reintroduced similar checks last year, along its borders with Austria, the Czech Republic, Poland and Switzerland.

Berlin said it had no choice, after successive years in which irregular arrivals from the Middle East and Africa have placed a strain on its infrastructure and the influx has led to the rise of the far right.

The border checks will be carried out during the coming six months while the government decides whether to make them permanent. It means all of Germany's land crossings are now subject to controls.

Interior Minister Nancy Faeser said the reintroduction of checks in some areas last year ensured more than 30,000 unauthorized entries were blocked.

"That is why we will expand our temporary border control to include all of Germany's land borders," Faeser said. "My order is also intended to protect against the acute threat of Islamist extremist terrorism and serious cross-border crime."

The checks will be carried out by police officers on a random basis, with most people still likely to flow through freely. Officers will target their checks based on information and the security situation, she said.

The Interior Ministry said travelers, even those from EU countries, should have valid identification and people from outside the EU will also need valid entry documents.

With a federal election due next year and the far right polling well, Svenja Niederfranke, an immigration expert at the German Council on Foreign Relations, told Euronews: "The German government wants to show that they are doing something… this is very important political signaling … that we take back control of our borders."

Poland's Prime Minister Donald Tusk criticized the move, saying more immigrants will settle in neighboring countries as a result. And Austria's Chancellor Karl Nehammer said it means his country will likely now also have to reintroduce checks, sending the EU's border-free ideal into tatters.

And as a potential row between Germany and the EU over the issue brews, the cost of the new checks has also been questioned, with one police union saying an additional 5,000 officers will be needed.