Twenty fire engines and 120 firefighters and officers have been called to a blaze on the roof of a hotel in Knightsbridge, central London, the London Fire Brigade said on Wednesday.

The cause of the blaze was not yet known, it added.

A Reuters reporter said smoke was visible coming from the five-star Mandarin Oriental hotel.

Police said the hotel was being evacuated and it was not yet known whether there had been any injuries.