Fire broke out at Londons Mandarin Oriental hotel on Tuesday, with dozens of firefighters deployed to tackle the blaze that pumped smoke high into the air over the British capital.
The fire brigade said "around 120 firefighters" and 20 fire engines were involved in tackling the fire on the roof of the 12-storey hotel in Knightsbridge, a luxury area of central London where Harrods department store is also located.
The fire service said the blaze was "producing a lot of smoke" and was "very visible" and its cause "is not known at this stage".
Firefighters were called to the fire at 1455 GMT.
"We are aware that there is a fire at Mandarin Oriental Hyde Park, London, and that the fire brigade is at the hotel," a hotel spokesman said.
"As the situation is still unfolding, we have no further details to share at this time, but will provide an update soon".
Roads were closed off at Scotch Corner and Hyde Park Corner, busy junctions near the hotel -- an Edwardian-style building that opened its doors in 1902 and was bought by Mandarin Oriental in 1996.
The hotel has 198 rooms and suites.
Transport for London, which manages the city's public transport system, said an entrance to Knightsbridge Underground station had been closed "at the request of the emergency services".
Anna Whiteley, a TV presenter, tweeted that she was evacuated from the hotel.
"Just evacuated Mandarin Oriental hotel to see this... absolutely crazy! So impressed by the organisation in bringing everyone to safety," she wrote on Twitter.
The London Ambulance Service said had sent "a number of resources" to the scene of the incident.