The demonstrations, which began in Istanbul on Wednesday, have since spread to more than 55 of Turkey’s 81 provinces, sparking clashes with riot police in the country’s worst street protests in more than a decade.
Imamoglu’s arrest — for “terrorism” and “corruption” — came just days before he was to have been formally named as the main opposition CHP’s candidate in the 2028 presidential race.
“Dictators are cowards!” and “AKP (Turkey’s ruling party), you will not silence us!” read some of the placards in the Istanbul protest on Saturday night, which appeared bigger and denser than the previous night.
Officers charged the City Hall gathering shortly after midnight (2100 GMT) using tear gas and forcing those who could to take refuge in the City Hall building.
Many were arrested, according to AFP journalists, but no official data was immediately available.
Riot police had earlier used rubber bullets, pepper spray and percussion grenades in clashes on the fringes of the rally, AFP correspondents said.
In the capital Ankara, riot police used water cannon to push back protesters, while in the western coastal city of Izmir police blocked a student march headed towards the local AKP offices.
CHP leader Ozgur Ozel, addressing the massed protesters in Istanbul, told them they numbered “more than half a million”.
He vowed the mobilisation would “defend” Imamoglu and march on the courthouse where the mayor had been taken late Saturday.
The mayor was taken to the courthouse, about 10 kilometres away from the City Hall demonstration, with 90 of his co-defendants, protected by dozens of riot vans and a heavy police cordon.
According to Imamoglu’s lawyers, his hearing on a “terrorism” charge concluded, while the hearing on a “corruption” charge was scheduled to follow in the middle of the night.
Police set up a tight security cordon around the courthouse while around 1,000 protesters stood nearby shouting slogans.
Earlier on Saturday, the 53-year-old mayor denounced the accusations against him as “immoral and baseless” in a statement released by City Hall.
“This process has not only harmed Turkey’s international reputation but has also shattered the public’s sense of justice and trust in the economy,” he said.
News of the mayor’s arrest badly hurt the lira and caused chaos on Turkey’s financial markets with the benchmark BIST 100 index closing Friday nearly 8.0 percent 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.
“Just as people took the streets to stand up for Erdogan after the July 15 (2016) coup, we are now taking to the streets for Imamoglu,” Cenk said.
“We are not the enemy of the state, but what is happening is unlawful.”
The unrest has spread rapidly despite a protest ban in Turkey’s three largest cities and a warning from Erdogan that the authorities would not tolerate “street terror”.
“For four days, they have been doing everything they can to disturb the peace and divide our people,” Erdogan said on Saturday.
“The days when politics and justice are guided by street terror are totally in the past,” he added.
Earlier in the evening, Istanbul Governor Davut Gul said the authorities would not allow anyone to enter or leave the city who was “likely to participate in illegal activities”.
Police have arrested 343 people since the start of the protests, the interior ministry said on Friday.
Turkey’s Journalists Union claimed the police had “deliberately targeted” journalists, saying many had been “severely beaten, shot with rubber bullets and had equipment broken”.
Despite Imamoglu’s detention, the CHP has vowed to press ahead with its primary on Sunday at which it would formally nominate him as the party’s presidential candidate.
It has pledged to open voting to anyone, not just party members, in the hope of garnering massive support for the beleaguered mayor, who is widely seen as the only politician capable of challenging Erdogan.
Observers said the government would likely seek to block the vote. (AFP)
