The foreign ministers of Germany and Turkey met in Berlin on Wednesday, the first meeting of government representatives since a diplomatic row about Turkish officials campaigning in the country and the arrest of journalist Deniz Yücel.

German Foreign Minister Sigmar Gabriel and his Turkish counterpart, Mevlüt Çavuşoğlu, discussed the diplomatic relationship between the two countries, which has become increasingly strained since Turkey's widespread purge of government critics in the wake of a failed coup.

Çavuşoğlu was in Germany to promote constitutional reform that would expand the powers of presidency and abolish the post of prime minister. Some 1.4 million Turks are eligible to vote in a referendum on the issue, which is scheduled for April 16.

Gabriel said Wednesday, while warning Ankara that comparisons to Nazis in any row is a "red line that cannot be crossed".

Despite the differences on both sides, "there is no alternative to dialogue because that is the only way we can return step by step to a normal and friendly relationship," he said.

In a statement after the meeting, Gabriel said he addressed the referendum, campaigning by Turkish ministers in Germany, as well as the arrest of German-Turkish journalist Deniz Yücel, which he referred to as "wrong and inappropriate." Turkey accuses Die Welt correspondent Yücel of links with the RedHack, a band of hackers known for their terror links, in addition to propaganda on behalf of the PKK terrorist group.

German local authorities have been cancelling the public appearances of Turkish ministers and government officials campaigning ahead of the April 16 referendum in several German towns and cities, based on poor excuses such as the inadequacy of parking lots and security concerns.

The meeting comes one day after Çavuşoğlu addressed fellow Turks outside his country's consulate in Hamburg as part of the government's bid to appeal to expatriate voters. The venue he had wanted to use cancelled citing fire safety concerns, which followed two other cancellations, prompting furious reactions from the Turkish minister.

Police and local authorities in Hamburg have already cancelled Çavuşoğlu's meetings two times.

Previously on Friday, Cologne authorities withdrew permission for a hall to be used for a speech by Economy Minister Nihat Zeybekci in Frechen on the outskirts of the city. Zeybekci later addressed Turks in Cologne on Sunday.

Last Thursday, German authorities also banned Justice Minister Bekir Bozdağ from meeting with Turks in the western German town of Gaggenau, citing inadequate meeting facilities and parking lots as excuses for the ban.

After his meeting with Gabriel, Çavuşoğlu is set to attend the International Travel Trade Show in Berlin to promote tourism to Turkey.