German Chancellor Angela Merkel has fiercely rejected comments made by Turkey’s President that Nazi practices were being used in her country.
Recep Tayyip Erdogan made the claims after rallies designed to woo Turkish voters in Germany ahead of a referendum were cancelled.
Some 1.4 million Turks who live in Germany can vote in Erdogan’s April referendum, which will grant the president more powers.
Relations have also soured following the detention of Turkish-German journalist Deniz Yücel in Istanbul.
Mrs Merkel said: “There are profound differences of points of view between Germany and Turkey on the state of liberty of the press and opinion in Turkey, on the destiny of many more than a hundred journalists in prison – also the destiny of our compatriot, the journalist Deniz Yücel.”
Demonstrations have been taking place around Germany in support of Mr Yücel.
The journalist for the newspaper Die Welt was arrested on charges of propaganda and incitement to hatred.
His supporters, who are also campaigning online, fear he could be held for up to five years before a trial.