Istanbul mayor Ekrem Imamoglu appeared before police for questioning on terror-related charges on Saturday, a day after his interrogation over corruption allegations.
His arrest earlier this week sparked protests across Turkey, with many demonstrators viewing his detention as a politically driven attempt to eliminate a key rival from the next presidential race.
Turkish Interior Minister Ali Yerlikaya said 343 suspects had been detained in protests across the country on Friday night, adding: "There will be no tolerance for those who seek to violate societal order, threaten the people's peace and security and pursue chaos and provocation."
Local media reported that police questioned Imamoglu for around five hours as part of an investigation into allegations of aiding the outlawed Kurdistan's Workers' Party, of PKK. On Friday he was questioned for four hours over corruption allegations.
Just before he was transferred to the courthouse, local authorities closed nearby roads and a large number of police were dispatched to the area.
Imamoglu is a popular opposition figure and seen as a major challenger to Turkish President Recep Tayyip Erdogan. He was detained on Wednesday following a dawn raid on his residence over allegations of financial crimes and links to Kurdish militants.
The mayor denied all charges put to him during both interrogations.
Many view the arrest as a politically driven attempt to remove a popular opposition figure and key challenger to Erdogan in the next presidential race, currently scheduled for 2028.
His arrest sparked protests that have steadily increased in intensity.
On Friday, police in Istanbul used pepper spray, tear gas and rubber bullets to push back hundreds of protesters who tried to break through a barricade in front of the city’s historic aqueduct while hurling flares, stones and other objects at officers.
Government officials reject accusations that legal actions against opposition figures are politically motivated and insist that Turkey’s courts operate independently.
