A motorcyclist has suffered serious burns following a three-vehicle collision in the Blue Mountains, north-west of Sydney.

Part of the Great Western Highway at in Blaxland has been closed after the crash involving a car, motorbike and a truck.

Fairfax reports that the car and motorcycle burst into flames at around 12.45pm this afternoon.

The motorcyclist was flown to Royal North Shore Hospital suffering burns to his legs, where he remains in a serious condition.

A 40-year-old woman has suffered burns to her arm and was reportedly taken to Nepean Hospital.

The Great Western Highway at Blaxland has been closed to westbound traffic, which is being diverted to Hope Street.