BERLIN (AP) — 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.

The conservative opposition leader tipped to lead Germany following next month's elections has promised far-reaching changes to border and asylum rules after a group of children were targeted in a deadly knife attack in Bavaria.