Twenty fire engines were dispatched to the fire, on William Street, after receiving more than 35 calls beginning at 3.55pm, London fire brigade said.
Crews from Chelsea, Kensington, Hammersmith, Battersea and surrounding fire stations attended the fire at the 12-storey luxury hotel. The London ambulance service attended the scene, but said there were no casualties “as far as we are aware”.
Large plumes of black smoke could be seen from across the capital rising above the building, which is close to Harrods department store and the One Hyde Park luxury apartment complex.
Flames could be seen around the top of the hotel, and extended ladders were erected to access that area of the building.
In a statement, the London fire brigade said: “The brigade was called at 3.55pm. Fire crews from Chelsea, Kensington, Hammersmith, Battersea and other surrounding fire stations are at the scene. The cause of the fire is not known at this stage.”
“The fire was in the middle of the hotel,” said Samir Boureghda, of Masgouf restaurant in William Street, who said it looked as if the flames had been extinguished.
A tradesman working at the hotel said he hit the alarm button when he saw a fire. The 19-year-old lift engineer, who gave his name as Harry, said: “I was in the lift shaft and I looked to my left and saw the geezers working on the roof. To my left there was a big fire. I said (to my colleague): ‘Lee, there’s a fire over there, let’s get out of the building. Get out the lift shaft, I’m being serious.’ We ran down the stairs and went and got the scaffolder out of the loading bay.”