(BBC) - At least 29 people have been killed and one injured in a fire in a nightclub in Turkey.

The Masquerade club, in the basement of a high-rise building in Istanbul, was closed and being renovated during the day.

The fire broke out just after midday, Istanbul governor Davut Gül said, adding that the cause was unclear.

Mr Gül said that the victims of the fire were thought to have been involved in the renovation work.

Five people have been arrested in connection with the fire as investigations continue.

They include three workplace officials, the nightclub manager and the manager of the renovations.

Firefighters and other first responders surrounded the charred and smoking entrance to the club, which occupies two floors underneath a 16-storey residential building in the city's Gayrettepe district.

The number of victims has rapidly increased throughout the afternoon, with the governor's office issuing a string of updates.

The newly re-elected Mayor of Istanbul, Ekrem Imamoglu, offered his condolences on social media.

"May God have mercy on our citizens who lost their lives, and I wish a speedy recovery to our injured," he said in a post on X, formerly Twitter.

Turkey's President, Recep Tayyip Erdogan, is aware of the tragedy following a phone call with interior minister Ali Yerlikaya.