Istanbul Mayor Ekrem Imamoglu is in custody after being detained on corruption and terror charges, which led to protests.

Turkiye has detained 37 people accused of sharing “provocative” social media posts over the detention of Istanbul Mayor Ekrem Imamoglu.

Imamoglu, President Recep Tayyip Erdogan’s main political rival, was taken into custody on Wednesday on charges including corruption and aiding a “terrorist” group – allegations he denies.

On Thursday, Interior Minister Ali Yerlikaya said 18.6 million posts were shared on X social media platform about Imamoglu within 24 hours of his detention.

He said authorities identified 261 social media accounts that shared provocative posts, inciting public hatred or crime. At least 37 of the suspected account users were detained in a police operation, Yerlikaya wrote on X.

Efforts to detain other suspects were continuing, he added.

Dozens of prominent figures, including journalists, businesspeople and Istanbul municipality staff, were also detained on Wednesday, leading to protests.

Protesters took to the streets and university campuses in various cities despite a four-day ban on gatherings imposed after Imamoglu’s detention.

As well as the ban on demonstrations, authorities closed several roads and restricted access to some social media platforms.

A construction company co-owned by Imamoglu was seized, the Istanbul chief public prosecutor’s office said. It said control of Imamoglu Construction, Trade and Industry was taken over by a court, based on financial crime investigation reports.

Government to ‘present solid evidence’

Imamoglu’s Republican People’s Party (CHP) represents the biggest political threat to Erdogan’s Justice and Development Party, or AK Party.

Imamoglu’s detention came just days before he was expected to be nominated as the CHP’s presidential candidate in a primary scheduled for Sunday. The party’s leader has said the primary will go ahead as planned.

CHP chairman Ozgur Ozel described Imamoglu’s detention as a “coup attempt” against the next president.

“Imamoglu won the mayoral elections [in Istanbul] twice – he won the last one with a huge margin of around 52 percent,” said Al Jazeera’s Sinem Koseoglu, reporting from Turkiye.

Koseoglu said, “He’s now in police custody and being accused of corruption and terrorism charges. According to judicial sources being cited in the media, there is a corruption of around $15bn which has been shared through Imamoglu and his entourage through municipality-affiliated companies. Government sources say they will present solid evidence about this.

“However, Imamoglu’s accusation of terrorism charges is an important step – if you are found guilty, you can be replaced by a government-appointed trustee. Many now suspect Imamoglu will now be replaced.”

Government critics see the detention as an effort to extend Erdogan’s more than two-decade rule following significant losses by the governing party in local elections last year.

For their part, government officials reject claims that crackdowns against opposition figures are politically motivated, and insist that the courts operate independently.

Elsewhere on Thursday, Russia said Imamoglu’s detention was the sovereign affair of Turkiye, while German Chancellor Olaf Scholz said the move was a “very bad sign” for Europe-Turkiye ties.

Turkiye’s next presidential vote is scheduled for 2028, but early elections are possible.