Update, 7.50pm: A motorcyclist is critically injured after being hit by a car in Henley Brook this afternoon.
The crash happened on Gnagara Road near the intersection of Henley Brook Avenue at about 4.30pm.
The male motorcyclist, who is believed to be in his mid-30's, is understood to have collided with a Mitsubishi Colt in front of a nearby shopping centre.
He has been taken to Royal Perth Hospital where he is in a critical condition.
The male driver of the car has not been seriously injured in the crash.
Police have urged motorists to avoid the area with traffic congested as a result of the crash.
Gnangara Road is closed in both directions in the area while police investigate the cause of the crash.
Police have asked to speak to the driver of a blue sedan who was in the area at the time of the crash. Those with information are asked to contact Crime Stoppers on 1800 333 000.