Ankara and Berlin are locked in a new dispute weighing on already frayed ties.

Chancellor Angela Merkel called for calm Monday in an escalating dispute with Turkey, a day after President Recep Tayyip Erdogan labelled a German ban on rallies by his ministers “Nazi practices.”

“To our Turkish partners, let us talk openly and critically, but let us remember the special meaning of our close relationship and let cool heads prevail,” said Merkel’s spokesman Steffen Seibert.

The spokesman sharply rejected Erdogan’s claim.

“Nazi comparisons are always absurd and out of place, because they lead only to one thing — the trivializing of the crimes against humanity committed by the Nazis,” said Seibert.

Ankara and Berlin are locked in a new dispute weighing on already frayed ties, this time over rallies in Germany by Turkish ministers to promote Erdogan’s bid for greater powers.

The row erupted late last week after three German local authorities banned ministers’ scheduled rallies ahead of an April referendum over the plan to scrap the prime minister post in Turkey altogether.