A fire that raged from the basement of a 16-storey block in central Istanbul left at least 29 people dead Tuesday, with flames and thick smoke billowing for hours despite a massive emergency response.

By late afternoon around 20 fire trucks and ambulances were still crowded around the building, where builders had been working on a nightclub in the basement.

A police cordon kept onlookers and traffic 100 meters (yards) away from the scorched facade, while an AFP reporter saw three exhausted firefighters sat on the ground with smoke-blackened faces and equipment.

The fire began at 12:47 (0947 GMT), the city governor's office said, but it was only in the late afternoon that Davut Gul's team announced the blaze was out.

As well as the 29 killed, one hurt person was still being treated in hospital, his office said.

It was not immediately clear whether the victims died from smoke inhalation or the flames.

"An investigation has been opened into the fire that occurred in Gayrettepe (neighborhood) in the Besiktas district of Istanbul," Interior Minister Ali Yerlikaya posted on X.

According to the governor's office, workmen had been renovating the basement nightclub when the fire broke out.

All the men working on the site were dead, the governor's office said, adding that it had "issued five arrest warrants", including for the club's owner and manager.

"Three of the suspects have been arrested and two more are being sought," it added.

  Mounting toll 

The authority had earlier reported that the fire broke out in the below-ground levels of the 16-storey block in Besiktas.

The toll rose throughout the afternoon, with most of the 12 people initially reported seriously hurt and then succumbing to their injuries despite hospital treatment.

"I've lost four friends," local man Fikret Kaya told AFP as firefighters were leaving the scene, but could not say any more.

Not far from him, a woman wearing a black cap was weeping with her head in her hands.

The venue, a popular Gayrettepe nightspot called "Club Masquerade", boasted several stages and regularly gave live concerts.

Its license was first issued in 1987 and renewed in 2018, governor Gul said, adding that the club was being "maintained and renovated".

TV images from the scene showed large flames roaring from lower-story windows, spewing a column of thick black smoke that hugged the building's facade.

Istanbul's newly re-elected mayor Ekrem Imamoglu, who rushed to the scene, said "The fire is under control. Let's hope there are no further victims", offering his "condolences" to the relatives of the dead and injured.