Turkey’s government criticised a call from the main opposition leader for people to take to the streets to protest what they say is the undemocratic detention of Istanbul’s mayor Ekrem Imamoglu, as thousands demonstrated across the country.

President Tayyip Erdogan’s main political rival, Imamoglu, was taken in on Wednesday facing charges of graft and aiding a terrorist group, in a move the opposition condemned as a “coup attempt”. It has sparked demonstrations at home, and criticism from European leaders.

On Thursday, some protestors clashed with police in Ankara, Izmir and Istanbul, including at universities, and many rallied at the municipal headquarters in Istanbul despite a 4-day ban on gatherings. Scattered protests took place across the country, as authorities erected barricades blocking several streets.

Speaking at a rally at the Istanbul Municipality building on Thursday, main opposition Republican People’s Party (CHP) leader Ozgur Ozel responded to Erdogan - who dismissed the opposition’s criticism as “theatrics” and “slogans” - saying Turks would not remain at home.

“Hey Erdogan, you’re most scared of the streets. We are now on the streets, in squares. Continue to be afraid,” Ozel said.

“While you keep the one we elected in custody, we will not sit at home,” he added.

“Mr. Tayyip, you are scared and you are asking ‘are you calling people to the streets? Are you calling people to the squares?’ Yes. I didn’t fill up these squares or these streets, you did.”

Interior Minister Ali Yerlikaya and Justice Minister Yilmaz Tunc criticised Ozel’s call, saying it was “irresponsible”.

“Gathering and marching in protest are fundamental rights. But calling to the streets over an ongoing legal investigation is illegal and unacceptable,” Tunc said on X after midnight on Thursday.

Tunc said the response to any legal process or decision must be given in the courtrooms and called for calm, adding that the “independent and unbiased judiciary” was evaluating the case.

The move against Imamoglu, the popular two-term mayor, comes as the CHP was set to announce him as its presidential candidate on Sunday, and caps a months-long crackdown on opposition figures that has been criticised as a politicised attempt to hurt their electoral prospects and silence dissent. The government denies this.

Since Imamoglu’s detention, supporters had called for more concrete action from Ozel and the CHP. Ozel told Reuters on Thursday that the CHP would demonstrate, but without disrupting public order.

He vowed to resist any potential attempts by authorities to remove him and CHP officials from the municipality headquarters, where they have been staying since Imamoglu’s detention, adding any appointment of a government trustee would be unjust and met with resistance.

A government appointee could replace Imamoglu if he is legally arrested as part of the probe charging him with aiding the PKK, which is deemed a terrorist organisation by Turkey and its Western allies.

His detention came a day after Istanbul University annulled his degree, which if upheld would block him from running for president.

The next presidential election is set for 2028 but Erdogan has reached his two-term limit as president after having earlier served as prime minister. If he wishes to run again, he must call an early election or change the constitution.