German Chancellor Angela Merkel lashed populists seeking to exploit Germany's refugee influx on Tuesday, but set down a tough line on integration - including a ban on the full-face veil - as she launched into election campaign mode.

Outlining a strategy to counter populism that has consumed key allies abroad, Merkel vowed there would be no repeat of last year's record refugee arrivals.

She also stressed it was legitimate for Germany to expect newcomers to integrate, and this included a rejection of the niqab full-face veil.