Friedrich Merz, currently leading in polls to become German chancellor, said Thursday if elected he will impose strict border controls.

A deadly knife attack on a kindergarten group in Germany, where an Afghan man was arrested at the scene, reignited a bitter immigration debate Thursday, a month before elections.

Germany's opposition leader vowed Thursday to bar people from entering the country without proper papers and to step up deportations if he is elected chancellor next month, as a knife attack by a rejected asylum-seeker spilled over into an election campaign in which he is the front-runner.