Tens of thousands of protesters have taken part in demonstrations across Turkey after the main rival to the country's President Recep Tayyip Erdogan was formally arrested and charged with corruption, BBC reports.
Ekrem Imamoglu, the mayor of Istanbul, was due to be selected as the Republican People's Party's (CHP) 2028 presidential nominee in a vote on Sunday.
In response to his arrest, Sunday night saw a ramping up of the worst unrest the country has seen in more than a decade - with protesters fired upon with tear gas and rubber bullets.
Imamoglu said the allegations against him are politically motivated. "I will never bow," he wrote on X before he was remanded in custody.
Erdogan has condemned the demonstrations and accused the CHP of trying to "disturb the peace and polarise our people".
Crowds amassed near Istanbul's city hall by early evening on Sunday for a fifth night, and could be seen waving Turkish flags and chanting in front of a row of riot police.
Officers were seen firing water cannons at some protesters and using pepper spray.
Imamoglu's wife Dilek Kaya Imamoglu addressed the large crowds outside the city hall, telling demonstrators that the "injustice" her husband has faced has "struck a chord with every conscience".
The demonstrations in response to Imamoglu's arrest are the largest the country has seen since the Gezi protests of 2013, which began in Istanbul over the demolition of a local park.
In total, rallies took place in at least 55 of Turkey's 81 provinces, or more than two-thirds of the country, according to a tally by French news agency AFP.
Imamoglu was one of more than 100 people, including other politicians, journalists and businessmen, detained as part of an investigation on Wednesday.
He was formally arrested on Sunday and charged with "establishing and managing a criminal organisation, taking bribes, extortion, unlawfully recording personal data and rigging a tender".
He was remanded in custody pending trial. AFP and local media reported he had been taken to a prison in Silivri.
Imamoglu has also been suspended from his post as mayor, Turkey's interior ministry said in a statement.
