At least six people were injured when a tornado swept through a residential street in north-west London this morning, tearing the roofs and walls off scores of houses.

The storm hit Chamberlayne Road, in Kensal Rise, at around 11am this morning. Eyewitnesses said the tornado lasted up to 40 seconds.

Colin Brewer, who lives in nearby Trevelyan Gardens, reported seeing trees collapsed in the road and people being hit on the head by flying objects, whiile Darma Vaja, who works close to the scene of the damage, said it was "like a minor explosion".

A spokesman for London Ambulance said six people were hurt. One man was taken to hospital with a head injury and five people were treated at the scene for minor injuries and shock.

Footage from a helicopter flying above the street showed part of the side of a house had collapsed into the road, partially covering a car parked outside. The footage shown on Sky News also showed several houses that had lost roofs.

Scotland Yard said the tornado had passed, but that the London Fire Brigade and ambulances were still Chamberlayne Road, which was closed.

Local resident Daniel Bidgood told radio station BBC London 94.9 said he was in his living room when he heard a big crack of lightning and thunder and heard a sound which he described as being "like standing behind a jetliner".

"I could see a huge cloud rolling up the street, making this tremendous sound," he said.

"I went to try to take a picture of it but a shower of debris smashed all the windows of my house."

Earlier a spokesman for London Ambulance Service said: "We have sent four ambulances, two fast response cars and two officers to the scene. We have also activated the helicopter emergency medical service, which carries a senior trauma-trained doctor and a paramedic."

A spokesman for weather forecaster MeteoGroup said a band of strong storms came through with Heathrow airport recording gusts of 55mph.

He said: "That is quite squally so residential areas might have had gusts of up to 60mph. That can cause some damage although it is hard to say at the moment whether it was definitely a tornado."

"From the damage it does look like it could be. It still seems to be very localised so it is either what is called a micro burst, a strong down burst of wind, or a tornado which is when the wind goes up."

Tim Klotz, who recently moved to the street, said the tornado had struck right in front of his house.

Mr Klotz said: "It was like some sort of cyclone. I was actually in an attic room, working at my desk on the computer, and there was heavy rain and sleet, and then the wind just really changed.

"I looked up through a skylight and debris was falling through the air. I heard what seemed like large, clay dominoes falling, which I think were roof tiles."

Until recently tornados were extremely rare in Britain. But in the last 18 months a number have arrived, prompting warnings that such freak weather events are likely to increase in frequency because of global warming.

In July 2005 a tornado in Birmingham damaged 1,000 buildings. And in October this year a tornado was reported just off Brighton, on the south coast.