İmamoğlu urged supporters to protest and defend democratic rights.
“I call on our nation to stand up for its rights with a sense of responsibility,” he wrote. “This fight for rights is about the future of our country and our children.”
He specifically called for demonstrations in Istanbul’s Saraçhane Square and in public squares across other cities.
“This is the day to stand up to those who steal the people’s will and to join the fight for justice,” he added.
On March 23, Turkish broadcaster Halk TV reported that a court had ordered İmamoğlu’s arrest. He is facing charges of corruption and alleged ties to terrorism, including connections to the Kurdistan Workers’ Party (PKK), which Turkey designates as a terrorist organization.
During his interrogation, İmamoğlu denied all allegations and rejected the testimony of anonymous witnesses.
President Recep Tayyip Erdoğan addressed the arrest on March 21, saying, “The problems of the Republican People's Party are not the problems of the country or the nation—they are the problems of a handful of dissenters in their headquarters.”
On March 20, authorities imposed a four-day ban on public gatherings in Istanbul in anticipation of unrest.
İmamoğlu, a senior figure in the opposition Republican People’s Party (CHP), is widely seen as one of Erdoğan’s strongest political rivals ahead of future national elections.