ISTANBUL — The leader of Turkey’s main opposition on Friday renewed a call on supporters to take to the streets for peaceful demonstrations against the arrest of Istanbul’s mayor and top rival to President Recep Tayyip Erdogan, even as authorities widened a ban on protests and criticized the appeal as irresponsible.

Mayor Ekrem Imamoglu was arrested in a dawn raid on his residence on Wednesday over alleged corruption and terror links, escalating a crackdown on opposition figures and dissenting voices. Several other prominent figures, including two district mayors, were also detained.

Many view the arrest as a politically driven attempt to remove a popular opposition figure and key challenger to Erdogan from the next presidential race, currently scheduled for 2028. Government officials reject accusations that legal actions against opposition figures are politically motivated and insist that Turkey’s courts operate independently.

Cumhuriyet newspaper and other media reported that police began questioning Imamoglu on Friday afternoon. The mayor can be detained without charges for up to four days.

Erdogan said that the government wouldn’t tolerate street protests and accused the opposition party of being associated with corruption, marginal groups and terrorist organizations.

“We see that an anti-corruption operation in Istanbul is being used as an excuse to stir unrest in our streets. I want it to be known that we will not allow a handful of opportunists to bring unrest to Turkey just to protect their plundering schemes,” Erdogan said.

“Pointing to the streets instead of courtrooms to defend theft, plunder, lawlessness and fraud is a grave irresponsibility,” Erdogan said. “Just as we have not surrendered to street terrorism until now, we will not bow to vandalism in the future either.”

Since Imamoglu’s arrest, thousands of people have gathered at Istanbul’s city hall for nighttime rallies, and clashes have erupted between demonstrators and police in Istanbul, Turkish capital Ankara and Turkey’s third-largest city, Izmir.

The most violent clash took place at Ankara’s Middle East Technical University late Thursday, when police deployed tear gas and water cannons to disperse the demonstration. Students said that rubber bullets were used, but the government has denied that.

The Interior Ministry said that more than 50 people were detained, and 16 police officers were injured, following the protests.

On Friday, authorities in Ankara and Izmir announced a five-day prohibition on demonstrations, following a similar ban imposed earlier by the Istanbul governor’s office. The bans came after the country’s justice minister acknowledged people’s right to demonstrate, but said that street protests amid ongoing judicial investigations were unacceptable.

Still, Ozgur Ozel, the chairman of the Republican People’s Party, CHP, made a new appeal for people to gather and demonstrate.

“I invite tens of thousands, hundreds of thousands, and millions to peacefully demonstrate, express our democratic reaction, and exercise our constitutional rights,” he said.

Ozel said: “To those who say that calling people to the streets is irresponsible, I say this: We are not the ones filling these streets and squares. It is your lawlessness and injustices that have brought people out.”

Imamoglu’s arrest came just days before he was expected to be nominated as the opposition Republican People’s Party’s presidential candidate in a primary on Sunday. Ozel has said that the primary, where around 1.5 million delegates can vote, will go ahead as planned.

The CHP has also urged citizens to participate in a symbolic election on Sunday — through ballot boxes to be set up across Turkey — to show solidarity with Imamoglu.

Analysts say Imamoglu could be removed from office and replaced by a “trustee mayor,” if he is formally charged with links to the outlawed Kurdistan Workers’ Party, or PKK, which is listed as a terrorist organization by Turkey and its Western allies.

Meanwhile, Ozel announced that the CHP has decided to hold an extraordinary party congress on April 6, to thwart an alleged attempt by the authorities to appoint a “trustee chairman” to lead the party. The decision came amid speculation that the authorities may be seeking to annul the party’s last congress held in 2023 over alleged vote-buying and other irregularities, and appoint a handpicked leader.

On Friday, the Borsa Istanbul’s benchmark index dropped by around 7%, prompting temporary trading suspensions aimed at preventing panic-driven sell-offs.