As police question the mayor, Turkey prepares for the fourth night of protests.

The arrest of Istanbul Mayor Ekrem Imamoglu sparked the largest street rallies the nation has witnessed in a decade, setting the stage for a fourth consecutive night of protests late Saturday.

Hundreds of thousands of people have taken to the streets in Turkey’s largest cities in a spectacular show of resistance, and officials reported 343 people have been detained in the protests.

Imamoglu, President Recep Tayyip Erdogan’s main opponent, was questioned by police on Saturday and was scheduled to meet with prosecutors later that day.

Days before he was officially announced as the major opposition CHP’s contender for the 2028 presidential election, he was detained on Wednesday.

Since then, riot police have engaged in many altercations with the demonstrators in Istanbul, the capital Ankara, and the western coastal city of Izmir, using water cannon, rubber bullets, and tear gas.

More than 50 of Turkey’s 81 provinces have seen protests, and Diyarbakir, the capital of the Kurdish-majority southeast, is anticipated to join the marches on Saturday.

Despite a ban on them and Erdogan’s warning that Turkish authorities would not tolerate “street terror,” the fresh demonstrations were anticipated to begin around 17:30 GMT on Saturday.

As part of a “terror” investigation, police spent five hours on Saturday interviewing the mayor of Istanbul. According to a source at City Hall, he was scheduled to meet with prosecutors in the Caglayan courthouse at 1630 GMT.

Imamoglu, who was overwhelmingly re-elected last year, has already been identified in an increasing number of court investigations on charges of “aiding and abetting a terrorist organization,” namely the outlawed Kurdish militant group PKK.

For “bribery, extortion, corruption, aggravated fraud, and illegally obtaining personal data for profit as part of a criminal organization,” he is also being investigated.

Authorities declared they were closing the key highways leading to the court a few hours prior to his arrival.