Il Nuovo Postiglione - Arrested Istanbul mayor urges judges to act as protests resume

Imamoglu urged judges and prosecutors to "stand up and take action against those who are ruining the judiciary" in a message on X via his lawyers.

"You cannot and must not remain silent," he wrote after spending his first night in police custody after what the main opposition CHP denounced as a political "coup".

The powerful and popular mayor -- who is President Recep Tayyip Erdogan's main political rival -- was held before dawn on Wednesday, just days before he was to be named as the CHP's candidate for the 2028 race.

The move brought thousands onto the streets, despite a four-day ban on protests, and by Thursday afternoon, the demonstrators were back holding placards saying "Together against lawlessness".

- 'Completely unlawful' -

More than 1,000 students from Galatasaray University joined a protest march through the waterfront Besiktas district, with scuffles as police tried to break it up, an AFP correspondent said.

Students were also marching from Istanbul University, which had on Tuesday revoked Imamoglu's degree -- a significant move as presidential candidates must have a third level qualification.

"The reason Erdogan did this is his fear of Imamoglu. It's completely unlawful," one 19-year-old student told AFP, declining to give his name.

CHP head and opposition leader Ozgur Ozel was expected to address protesters at City Hall again on Thursday at 1730 GMT, a party spokesman told AFP.

The move against Imamoglu sent Turkey's financial markets into a tailspin, dealing a heavy blow to the Turkish lira that was trading at around 38 lira to the dollar on Thursday.

Turkey's Central Bank said it would draw on its foreign exchange reserves if needed to prevent further harm to the currency, with economists saying it had already done so on Wednesday.

- Round-ups -

More than 80 people were rounded up in Wednesday's raids and investigators began quizzing them early on Thursday, local media said.

Already named in a growing list of legal probes, Imamoglu -- who was resoundingly re-elected last year -- has been accused of "aiding and abetting a terrorist organisation" -- namely the banned Kurdish militant group PKK.

He is also under investigation for "bribery, extortion, corruption, aggravated fraud, and illegally obtaining personal data for profit as part of a criminal organisation" along with 99 other suspects.

Social media and internet access, which was blocked early on Wednesday, remained largely restricted in Istanbul on Thursday morning, according to online censorship monitor Free Web Turkey.

Interior Minister Ali Yerlikaya said 37 people had been detained for posting content online that was deemed "provocative" and more investigations were under way.

- Weaponising the justice system -

"Imamoglu's only crime was that he was taking the lead in opinion polls," CHP leader Ozel told the crowds at Wednesday night's protest.

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

Human Rights Watch called for Imamoglu to be "released from police custody immediately".

"The Erdogan presidency should ensure that the results of the Istanbul municipal elections are respected and that the criminal justice system is not weaponised for political ends," said its Europe and Central Asia director Hugh Williamson.

By law, Erdogan -- who has been president for more than a decade, having been premier for 11 years before that -- cannot run again in the 2028 race.

But he wants to change the constitution to allow that, a move that requires opposition support.

Hamish Kinnear, a senior analyst with Verisk Maplecroft risk consultancy, said the move against Imamoglu could end up harming those plans.

"It could upset the government's plan to push through constitutional change that would enable Erdogan to run for a third term," he said.

Erdogan already changed the constitution to introduce the presidential system after a referendum in 2017.

F.Ciambrone--INP