Volkswacht Bodensee - Istanbul's mayor still held as new rally called

Imamoglu is President Recep Tayyip Erdogan's main political rival and his detention came just days before the party was expected to name him as its candidate for the 2028 presidential election.

Financial markets in Turkey fell shortly afterwards in what analysts said indicates investors' serious concerns that the move was politically motivated.

The leader of the main opposition CHP, of which the mayor is a member, is expected to address supporters outside Istanbul's City Hall at 1730 GMT on Thursday, a party spokesman told AFP.

University students also planned several demonstrations in the city.

The governor has banned all protests in Istanbul for four days.

Hundreds of police joined the pre-dawn raid on Imamoglu's home in Istanbul on Wednesday, he posted on X before being taken away, with the authorities then blocking access to social networks.

Access to the internet and social media was still slow early Thursday.

Thousands of angry protesters gathered outside City Hall late on Wednesday, chanting slogans including "Erdogan, dictator!" and "Government, resign!"

Already facing an array of legal battles, the two-time Istanbul mayor is now under investigation for "aiding and abetting a terrorist organisation" -- namely the banned Kurdish militant group PKK.

He is also being probed for "bribery, extortion, corruption, aggravated fraud, and illegally obtaining personal data for profit as part of a criminal organisation" along with around 100 other suspects.

- Backlash -

CHP leader Ozgur Ozel, who travelled from Ankara to Istanbul immediately after the mayor was held, branded it a "coup" as he attended Wednesday night's protest.

"Imamoglu's only crime was that he was taking the lead in opinion polls," he said alongside Imamoglu's wife Dilek.

"His only crime was that he won the hearts of the people. His only crime was he would be the next president," he added.

Local media said the other suspects were being interrogated at police headquarters but that Imamoglu has not yet been questioned.

Hamish Kinnear, a senior analyst with Verisk Maplecroft, a risk consultancy, said the arrest had sparked "a heightened risk of civil unrest, which the government appears to have anticipated by introducing a four-day ban on protests in Istanbul."

The analyst warned Imamoglu's detention could spoil the government plans to change the constitution so that Erdogan can run another term.

"If Imamoglu's arrest unites the opposition and provokes a political backlash, it could upset the government's plan to push through constitutional change that would enable Erdogan to run for a third term," he said.

Under the constitution, Erdogan -- who has been president for more than a decade -- cannot run again for the presidency. He already changed the constitution to introduce the presidential system after serving as prime minister for 11 years.

The Turkish lira fell sharply against the dollar after Imamoglu's detention, trading at 37.99 on Thursday morning.

L.Meier--VB