A court in Istanbul has formally remanded the city's mayor, Ekrem Imamoglu, in custody as part of a bribery investigation.

Four days ago, his detention sparked Turkey's biggest protests in more than a decade.

The mayor is one of 100 people being investigated on corruption charges and is also being investigated in a second case on "terrorism"-related charges. The court is due to rule on him in the coming hours.

The popular opposition mayor, who is President Recep Tayyip Erdogan's biggest political rival, was arrested just days before he was to be announced as the main opposition party's candidate for the 2028 presidential race. 

He was detained in connection with two investigations into bribery and "supporting a terrorist organisation" - charges he called "immoral and baseless". 

The measure against him sparked protests in Istanbul that have since spread to more than 55 of Turkey's 81 provinces, sparking battles with police. 

Following another mass protest late Saturday, police arrested 323 people, Interior Minister Ali Erlikaya wrote in X. 

The Republican People's Party went ahead with its long-planned primary for presidential candidates, which began at 8:00 a.m. local time. 

The party opened voting to anyone, not just its own members, hoping for mass support for the outspoken mayor who is considered the only politician capable of defeating Erdogan. | BGNES, AFP