It also caused a shockwave in the financial market, triggering temporary halts in trading on Wednesday to prevent panic selling.

German Chancellor Olaf Scholz expressed concern over the mayor’s detention, saying it was a “very, very bad sign” for Turkey’s relations with the European Union.

Imamoglu was elected mayor of Turkey’s largest city in March 2019, a historic blow to Erdogan and the president’s Justice and Development Party, which had controlled Istanbul for a quarter-century. Erdogan’s party pushed to void the municipal election results in the city of 16 million, alleging irregularities.

The challenge resulted in a repeat of the election a few months later, which Imamoglu also won. The mayor retained his seat following local elections last year, during which his party made significant gains against Erdogan’s governing party.