Flames and smoke billow as firefighters deal with a serious fire in a tower block at Latimer Road in West London, Britain June 14, 2017. [Photo by Lei Xiaoxun/chinadaily.com.cn]

"This is a large and very serious incident and we have deployed numerous resources and specialist appliances."

More than 20 ambulance crews were at the scene. London Mayor Sadiq Khan said a "major incident" had been declared. Police closed the A40, a major road leading out of west London, while some parts London's underground train network were closed as a precaution.

The cause of the fire, which broke out just before 1 am (0000 GMT), is not known, the Fire Brigade said. Residents said repairs, including the addition of some sort of cladding, had been made to the exterior of the block recently.