A Turkish court on Sunday jailed Istanbul Mayor Ekrem Imamoglu, President Tayyip Erdogan's main political rival, pending trial on corruption charges.
The decision to send Mr Imamoglu to jail comes after the main opposition party, European leaders and tens of thousands of protesters criticised the actions against him as politicised and undemocratic.
A Turkish court is also due to rule on a second "terror-related" probe into the popular opposition mayor, whose detention has sparked the country's worst street protests in more than a decade.
Following Mr Imamoglu's arrest, he called on Turks to continue to hold mass demonstrations across the country against his pending trial.
In a post on X, Mr Imamoglu said the legal process over his detention was "a complete extrajudicial execution" which meant a "betrayal against Türkiye."
Before Mr Imamgolu spoke out against his arrest, the main opposition Republican People's Party (CHP) wrote "No despair! Keep fighting!" on X.
CHP also denounced the arrest as "a political coup d'etat", meaning a sudden overthrow of the government by a small group.
The news came as voters cast their ballots in a CHP primary to name Mr Imamoglu the party's candidate for the 2028 presidential race.
The long-planned vote was the event which triggered the arrest of Mr Imamoglu, who is widely seen as the only politician capable of challenging President Recep Tayyip Erdogan.
He was detained in connection with two probes alleging graft and "aiding a terror organisation" — accusations that he told police were "immoral and baseless".
The move against him sparked protests in Istanbul that have since spread to more than 55 of Turkey's 81 provinces, unleashing running battles with police, who arrested 323 people overnight, officials said.
What happened during the protests?
During the protests, police used rubber bullets, pepper spray and percussion grenades on the protesters, toughening their methods throughout the night and forcing people to take refuge inside a city hall building, an AFP correspondent said.
In the capital Ankara, police used a water cannon to push back protesters, while in the western coastal city of Izmir police blocked a student march headed towards the local offices of the ruling AKP party.
"Dictators are cowards!" and "AKP, you will not silence us!" read some protesters' placards.
The nightly protests began shortly after Imamoglu was taken to the courthouse to answer prosecutors' questions in the two investigations.
Police set up a tight security barrier around the courthouse, where around 1,000 protesters stood nearby shouting slogans, an AFP correspondent said.
The CHP said the vote was open to everyone, not just members, in the hope of a massive show of support for Mr Imamoglu.
"We will, hand in hand, uproot this blow, this black stain on our democracy," Mr Imamoglu wrote in a post on X.
"I am standing tall, I will not bow down."
The opposition leader and CHP head Ozgur Ozel said the Istanbul council would now elect someone to work as acting mayor while they await a ruling on Mr Imamoglu.
Mr Imamoglu's legal team is set to appeal the court decision.
Turkish lira slides
On Saturday, the 53-year-old mayor denied the charges against him, telling police his arrest had done untold damage to Türkiye's image, in a statement released by City Hall.
"This process has not only harmed Türkiye's international reputation but has also shattered the public's sense of justice and trust in the economy," he said.
The move against him badly hurt the lira and caused chaos in Türkiye's financial markets, with the benchmark BIST 100 index closing on Friday nearly eight per cent lower.
"We are here today to stand up for the candidate we voted for," 30-year-old Aykut Cenk told AFP outside the court, holding a Turkish flag.
"We are not the enemy of the state, but what is happening is unlawful."
The unrest has spread rapidly despite a protest ban in Türkiye's three largest cities and a warning from Mr Erdogan that authorities would not tolerate "street terror".
Wires
