Hundreds of supporters gathered outside Silivri prison, west of Istanbul, where the hearing was taking place. Mayor Ekrem Imamoglu has been held at Silivri since March 23. The case alleges that he threatened a public prosecutor and is one of six that predate his arrest last month, which led to nationwide protests.

Ekrem Imamoglu's hearing centers on insulting and threatening the chief Istanbul prosecutor. His imprisonment over unrelated charges of corruption and aiding a terrorist group sparked mass protests across Turkey.

Imamoglu is being held on corruption and terrorism charges, but appeared in a special court at Silivri jail in a separate case on Friday accused of trying to intimidate Istanbul's chief prosecutor. Turkey's opposition has condemned Imamoglu's arrest as a "coup attempt against our next president" and his detention has prompted the biggest anti-Erdogan protests in more than a decade.