The main rival to Turkey?s President Recep Tayyip Erdogan has been formally arrested and charged with corruption.

Ekrem Imamoglu, the mayor of Istanbul, is expected to be selected as the opposition Republican People?s Party?s (CHP) 2028 presidential nominee in a ballot on Sunday.

He has denied the allegations and said they are politically motivated. ?I will never bow,? he wrote on X before he was remanded in custody.

His detention sparked some of Turkey?s largest protests in more than a decade. Erdogan has condemned the demonstrations and accused the CHP of trying to ?disturb the peace and polarise our people?.

Imamoglu was one of more than 100 people, including other politicians, journalists and businessmen, detained as part of an investigation on Wednesday, triggering four consecutive nights of demonstrations.

On Sunday, he was formally arrested 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.

In social media posts, Imamoglu criticised his arrest as a ?black stain on our democracy?, and said judicial procedure was not being followed.

He urged people across the country to join protests and to take part in Sunday?s vote. Imamoglu is the only person running in the CHP?s presidential candidate selection.

Large crowds had already gathered near Istanbul?s city hall by early evening, and could be seen waving Turkish flags and chanting in front of a row of riot police.

As night began to fall, officers were seen firing water cannons at some protesters.

The arrest does not prevent Imamoglu?s candidacy and election as president, but if he is convicted of any of the charges against him, he will not be able to run.

The jailed politician is seen as one of the most formidable rivals of Erdogan, who has held office in Turkey for 22 years as both prime minister and president.

However, due to term limits, Erdogan cannot run for office again in 2028 unless he changes the constitution.

Opposition figures say the arrests are politically motivated. But the Ministry of Justice has criticised those connecting Erdogan to the arrests, and insist on its judicial independence.

Imamoglu has meanwhile been suspended from his post as Instanbul?s mayor, Turkey?s interior ministry said in a statement.

Prosecutors also want to charge Imamoglu with ?aiding an armed terrorist organisation?, but the Turkish court said it was not currently necessary.

The CHP had a de facto alliance with the pro-Kurdish Peoples? Equality and Democracy Party (DEM) in connection with last year?s local elections.

DEM has been accused of being affiliated with the PKK ? or Kurdistan Workers? Party ? which it denies.

The PKK declared a ceasefire early this month, after waging an insurgency against Turkey for more than 40 years. It is proscribed as a terrorist group in Turkey, the EU, UK and US.

Meanwhile, Istanbul University announced on Tuesday it was revoking Imamoglu?s degree due to alleged irregularities.

If upheld, this would put his ability to run as president into doubt, since the Turkish constitution says presidents must have completed higher education to hold office.

Imamoglu?s lawyers said they would appeal the decision to revoke his degree to the Constitutional Court and the European Court of Human Rights.

The Supreme Election Council will decide whether Imamoglu is qualified to be a candidate.

Thousands have taken to the streets across Turkey in largely peaceful demonstrations since Imamoglu?s detention on Wednesday.

An initial four-day ban on gatherings in Istanbul, designed to stifle protests, now covers the whole country. It was extended for another four days on Saturday.

More than 700 arrests have been made since the protests began, according to Turkish authorities.

Riot police have repeatedly clashed with protesters and have been seen firing pepper gas and water cannons towards them.

On Saturday, tear gas hung in the air outside the mayor?s office in Istanbul before the protests had even started.

As the crowds grew throughout the evening, it became hard to breathe as round after round was fired to disperse demonstrators.

Chanting ?rights, law, justice?, people of all ages defied the government ban to protest against what they saw as an unlawful detention.

One young woman, dressed in black and wearing a face mask, told the BBC she was not protesting for political reasons or because she supported the opposition, but instead to defend democracy.

?I?m here for justice, I?m here for liberty. We?re free people and Turkish people cannot accept this. This is against our behaviour and culture.?

Another woman, who had brought her 11-year-old son to the protests, said she wanted to include him because she is worried about his future.

?It?s getting harder to live in Turkey day by day, we can?t control our lives, we can?t choose who we want and there is no real justice here,? she said. (BBC: Text, Excluding Headline)

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