President Recep Tayyip Erdogan has condemned growing protests in Turkey days after the arrest of a key opposition figure.

In a speech on Friday, Erdogan said his government would not “surrender” to “vandalism” or “street terror” ahead of more protests. “We will not accept the disruption of public order.”

On Wednesday, police detained Istanbul’s mayor, Ekrem Imamoglu, on charges of corruption and aiding terrorist groups, days before he was due to be selected as a presidential candidate.

Protesters took to the streets on Friday for a third day, despite bans on demonstrations, after the interior minister said 53 people were arrested at protests on Thursday.

Imamoglu, who is from the secular Republican People’s Party (CHP), is seen as one of President Recep Tayyip Erdogan’s strongest political rivals.

His arrest came just days before he was expected to be announced as a candidate for the 2028 presidential election.

He was one of more than 100 people – including other politicians, journalists and businessmen – detained as part of the investigation.

Thousands gathered in protest in Istanbul on Friday. Riot police reportedly fired rubber bullets and pepper gas as they clashed with hundreds of demonstrators. Other clashes were reported in Izmir.

Ozgur Ozel, the leader of CHP, had called for the third nightly protest outside Istanbul’s city hall at 20:30 local time (17:30 GMT) and said the president was afraid of the protests.

He also asked people elsewhere in Turkey to demonstrate peacefully at the same time, wherever they are in the country.

“Break down those barricades without harming the police, take to the streets and squares,” he said.

Authorities tried to stifle the street demonstrations with a four-day ban on all gatherings in Istanbul, announced straight after the arrests on Wednesday.

They have since extended this order to Ankara and the western coastal city of Izmir as protests have spread, with tens of thousands gathering across Turkey.

Ahead of Friday’s protests, Istanbul’s pro-Erdogan governor ordered the closure of the Galata and Ataturk bridges, both of which cross the Golden Horn estuary to where city hall is located.

Interior minister Ali Yerlikaya has similarly criticised the demonstrations, calling the opposition “irresponsible”.

Another 54 people have been arrested for violating a law on “inciting the public to hatred and hostility” by posting online, he said.

Yerlikaya added that 16 police officers have been injured in the demonstrations.

The arrests of Imamoglu and others follow a major nationwide crackdown in recent months, targeting opposition politicians, journalists and figures in the entertainment industry.

Opposition figures say the arrests are politically motivated. But the justice ministry has criticised those who link Erdogan to the arrests, and insist on their judicial independence.

Imamoglu won a second term as Istanbul’s mayor last year, when his CHP party swept local elections there and in Ankara.

It was the first time since Erdogan came to power that his party was defeated across the country at the ballot box.

The elections were also a personal blow to the president, who grew up in and became mayor of Istanbul on his rise to power.

Erdogan has held office for the past 22 years, as both prime minister and president of Turkey. Due to term limits, he cannot run for office again in 2028 unless he changes the constitution.

The CHP’s presidential candidate selection, in which 1.5 million members will vote and Imamoglu is the only person running, is set to take place on Sunday.

The party has also called on citizens to vote in a symbolic election, with plans to place ballot boxes in districts all over Turkey for people to show their support for the detained mayor.