The Istanbul stock exchange's main index was hit hard on Friday, closing 7.8 percent down on the third day of protests over the arrest of Istanbul mayor Ekrem Imamoglu.
The 53-year-old mayor -- Erdogan's main political rival -- was arrested on Wednesday, days before he was due to be named the CHP party's candidate for the 2028 presidential race.
The BIST 100 had already slipped by 8.7 percent on Wednesday following Imamoglu's arrest over allegations of "corruption" and links to a "terrorist organization".
The damage was limited to a fall of 0.5 percent on Thursday, but faced with a sharp fall on Friday, trading was suspended twice in the morning.
The index fell below 9,000 points during Friday trading for the first time since early November, a fall of more than 16.5 percent over five days.
Imamoglu's party has denounced his arrest as a "coup" and international organizations including the European Union have expressed concern.
It has also sparked street protests, which President Recep Tayyip Erdogan on Friday denounced as "street terror".
