Sixty firefighters were tackling a major blaze in an office building in London's fashionable Soho district, a fire brigade spokesman said.

"Seventy-five percent of the building has been destroyed," the spokesman said. "It's still an active fire."

The building had a basement, ground floor and four upper storeys, he added.

The fire broke out in Dean Street, a street lined with restaurants and bars, at lunchtime on Friday. Diners were evacuated and a huge pall of black smoke hung over the area.

There were no reports of anyone being trapped in the buildings, the spokesman said.