Turkiye was headed for a fourth straight night of protests late on Saturday, as the biggest street unrest the country has seen in over a decade raged on over the arrest of Istanbul Mayor Ekrem Imamoglu.

Officials said 343 people have been arrested in the demonstrations, which have seen hundreds of thousands hit the streets in Turkiye’s biggest cities in a massive show of defiance.

Imamoglu, the main rival of President Recep Tayyip Erdogan, was interrogated by police today and was due to appear before prosecutors later in the day.

He was arrested on Wednesday, days before he was to be formally named the main opposition CHP’s candidate for the 2028 presidential race.

Riot police have since then clashed repeatedly with the protesters, deploying tear gas, rubber bullets and water cannons against them in Istanbul, the capital Ankara and the western coastal city of Izmir.

The demonstrations have spread to more than 50 of Turkiye’s 81 provinces, with Diyarbakir, the main city in the Kurdish-majority southeast expected to join Saturday’s rallies.

The renewed protests were expected at 1730 GMT today, despite a ban on them and Erdogan’s warning that Turkish authorities would not tolerate “street terror”.

Police interviewed the Istanbul mayor for five hours today in connection with a “terror” probe. He was to appear before prosecutors at the Caglayan courthouse at 1630 GMT, a source at City Hall said.

Already named in a growing list of legal probes, Imamoglu — who was resoundingly re-elected last year — has been accused of “aiding and abetting a terrorist organisation”, namely the banned Kurdish PKK.

He is also under investigation for “bribery, extortion, corruption, aggravated fraud, and illegally obtaining personal data for profit as part of a criminal organisation”.

Several hours before his appearance, the authorities announced they were sealing off the main roads leading to the court.

‘No explanation’

“Mr Imamoglu denies all the charges against him,” one of his lawyers, Mehmet Pehlivan said, after the mayor on Friday was questioned for six hours by police over the graft allegation.

In a message on X sent via his lawyers, Imamoglu said he was “honoured and proud” of the demonstrators who were “protecting our republic, our democracy, the future of a just Turkiye, and the will of our nation”.

The pro-Kurdish opposition DEM party, which has had 10 of its own elected mayors removed over the past year and replaced by government-appointed trustees has also thrown its support behind the protests.

“There is no explanation for this action against [someone] elected by millions of Istanbulites … We want Ekrem Imamoglu … and the other mayors returned to their posts and we will continue to struggle for this,” said DEM lawmaker Meral Danis Bestas.

Addressing the crowds outside City Hall late on Friday, CHP leader Ozgur Ozel said 300,000 people had joined the demonstration that night.

Several hours earlier, Erdogan had fired a warning shot across Ozel’s bows, accusing him of “grave irresponsibility”, raising the prospect that the CHP leader too could face legal sanction.

“Those who provoke our citizens and cause them to clash with our security forces are committing a clear crime,” wrote Istanbul Governor Davut Gul said on X today.

The move against Imamoglu has hurt the Turkish lira and financial markets, with the stock exchange’s BIST 100 index closing down nearly eight per cent on Friday.