Germany has announced plans to tighten control at all of its land borders as part of a crackdown on migration, placing restrictions on a wide area of free movement known as the Schengen Zone.

Germany reintroduced temporary controls on its western and northern borders on Monday as part of efforts to combat irregular migration and cross-border crime, the interior ministry said.

Polish Prime Minister Donald Tusk on Tuesday condemned neighboring Germany’s decision to tighten border controls in its bid to clamp down on irregular migration. “From the Polish point of view, this type of action is unacceptable,” Tusk said during a meeting of Polish diplomats.