Turkish government representatives have addressed their supporters in Germany in person several times in recent years.
Appearances by former prime minister and current President Recep Tayyip Erdogan have come in for particular criticism.
February 10, 2008: Erdogan warns Turks in Germany against too much assimilation. “Assimilation is a crime against humanity,” he said, addressing around 16,000 supporters in the western city of Cologne.
February 27, 2011: Speaking in front of around 10,000 people in Dusseldorf, Erdogan calls on his compatriots to integrate, but once again rejects complete assimilation: “Our children must learn German, but they must learn Turkish first.”
February 4, 2014: Erdogan calls for support in the forthcoming presidential election at an event with an audience of around 4,000 in Berlin.
May 24, 2014: After the mine disaster in Soma, Turkey, Erdogan criticized reporting in Germany in front of around 15,000 supporters in Cologne, and campaigns for the presidential election. At the same time, around 45,000 counter-demonstrators marched through the city centre.
January 12, 2015: The then prime minister Ahmet Davutoglu calls for more determination in the fight against racism, in front of around 3,000 supporters of the Justice and Development Party (AKP) in Berlin.
May 10, 2015: Ahead of parliamentary elections in Turkey, President Erdogan calls for people with a migrant background to integrate, but preserve the values, religion and language of their homeland, in front of around 14,000 supporters in the southern city of Karlsruhe.
July 31, 2016: Around two weeks after the failed coup in Turkey, Sports Minister Akif Cagatay Kilic speaks to 40,000 people at a pro-Erdogan demonstration in Cologne.
A live video of the president on a big screen was banned due to the heated mood.
February 18, 2017: Prime Minister Binali Yildirim campaigns for the introduction of a presidential system in Turkey, in front of around 10,000 people in the western city of Oberhausen.
March 2, 2017: The south-western town of Gaggenau prohibits Turkish Justice Minister Bekir Bozdag from making a campaign appearance for security reasons.
The city of Cologne denies a request for an appearance by Economy Minister Nihat Zeybekci. The next day, an appearance by Zeybekci in nearby Frechen was also prohibited.
An event at the Senats hotel in the city was expected to go ahead on Sunday.