An Istanbul court on Wednesday sentenced Istanbul Mayor Ekrem Imamoglu, the main rival of Turkey’s President Tayyip Erdogan, to a fresh prison term, state broadcaster TRT reported, extending a crackdown on the opposition.

Imamoglu, who has been in jail pending trial since March over separate corruption charges, was sentenced to one year and eight months in prison for insulting and threatening the chief Istanbul prosecutor.

The prison sentence must be confirmed by two appeals courts.

It’s the second time Imamoglu has been convicted of insulting public officials. In 2022, Imamoglu was sentenced to two years and six months in jail for criticising election board officials over a decision to cancel 2019 Istanbul elections, in which he defeated the ruling AK Party candidate. He has appealed that sentence but it has not yet been reviewed.

Imamoglu denies the charges.

“I’ve been fighting against the abuse of the judiciary and against its use as a political tool. This is indeed an insult against our nation,” Imamoglu was quoted as saying by broadcaster Halk TV and other Turkish media.

The 2022 conviction, if upheld, could prevent Imamoglu from participating in future elections. Istanbul University in March annulled Imamoglu’s university diploma, without which he cannot stand as a candidate for president.

Since October last year, police have detained more than 500 people, over 200 of whom were then jailed pending trial, under investigations into municipalities run by the main opposition CHP, Imamoglu’s party.

The CHP denies corruption allegations and calls them a politicised attempt by the government to remove electoral threats against Erdogan, a charge the government rejects.

Wednesday’s hearing was held inside a courthouse-prison complex in Istanbul’s Silivri district, a site often used for high-profile and politically sensitive trials and where Imamoglu is currently being held.