Chancellor Angela Merkel on Monday sought to calm an escalating row with Turkey, a day after President Recep Tayyip Erdogan labelled a German ban on rallies by his ministers "Nazi practices".
But yet another event cancellation -- of a speech Foreign Minister Mevlut Cavusoglu had planned to give Tuesday in Hamburg, on fire safety grounds -- only threatened to reignite the dispute.
Merkel's office, while firmly rejecting Erdogan's Nazi jibe as "absurd and out of place," sought to draw a line under the spat that is further fraying ties between the two countries.
"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," Merkel's spokesman Steffen Seibert said.
Sharply rejecting Erdogan's comments, he added: "Nazi comparisons are always absurd and out of place, because they lead only to one thing -- the trivialising of the crimes against humanity committed by the Nazis."
The row erupted late last week after three local German authorities banned Turkish ministers' scheduled appearances ahead of an April referendum on a plan to scrap the prime minister post in Turkey, thereby boosting Erdogan's powers.
The German authorities cited capacity and security problems in hosting the events, which they said were likely to attract large crowds.
Merkel has said her government did not have a hand in the decisions, which fell under the jurisdiction of local officials.
But Ankara responded with fury to the cancellations, accusing Berlin of working against the referendum.
- Erdogan warns Germany -
On Sunday, Erdogan told a rally in Istanbul: "Germany, you are not even close to democracy. Your practices are not different from the Nazi practices of the past."
He also warned Germany not to hinder him from making an appearance if he wished.
"If you don't let me in, or if you don't let me speak, I will make the whole world rise up," he said.
Cavusoglu pressed the attack on Monday, accusing Berlin of working to scupper the rallies.
"The hotels, the conference halls are being put under pressure, police are being sent to the owners of these places: it's systematic pressure, a manoeuvre aimed at erecting systematic barriers," said the foreign minister.
"The state and the state-run institutions are all implicated. That's unacceptable. As for us, we will take the necessary measures, we have no fear of anyone," said Cavusoglu.
Hours later police in the northern city of Hamburg said the venue where Cavusoglu had planned to speak Tuesday could not be used "after serious fire safety deficiencies were identified".
"It's not the event that was cancelled, but the use of the Plaza Event Center," a police spokesman told AFP.
Turkey's state news agency Anadolu said the rally would go ahead in another venue, as Prime Minister Binali Yildirim said he hoped there would be "no further escalation".
On Wednesday in Berlin, Cavusoglu is scheduled to meet his German counterpart, Sigmar Gabriel.
- Tensions spilling over -
Germany is home to the biggest population of Turkish people abroad with about three million people of Turkish origin, the legacy of an extensive "guest worker" programme in the 1960s and 70s.
With some 1.4 million Turks in Germany holding the right to vote in Turkey, it is not uncommon to see politicians travelling from Ankara to try to sway voters.
Undeterred by the cancellations last week, Turkish Economy Minister Nihat Zeybekci made a campaign appearance in Cologne on Sunday.
Seibert repeated Merkel's stance that campaign rallies by Turkish ministers, in general, "are possible within rules and regulations".
Ankara-Berlin ties have been strained by a series of disputes, particularly since the failed coup against Erdogan in July.
Berlin has emerged as a strident critic of Ankara's post-coup crackdown, which has seen more than 100,000 people arrested or dismissed from their posts over alleged links to the plotters or to Kurdish militants.
Given the significant Turkish and Kurdish populations in Germany, Berlin is anxious to prevent Turkish domestic disputes from spilling into the country.
Most recently, Ankara's arrest of Deniz Yucel, a Turkish-German dual national who is a correspondent for Germany's Die Welt newspaper, has sparked an outcry in Berlin.
An Istanbul court has charged Yucel with spreading terrorist propaganda and inciting hatred.