Biker seriously hurt in Sydney smash

A 51-year-old motorbike rider has been seriously injured after colliding with a car at a suburban Sydney roundabout.

The rider suffered serious chest, head and lower leg injuries in the collision in Blacktown at around 3.30pm on Saturday.

A medical team aboard a rescue helicopter treated the man at the scene before he was stabilised and taken by ambulance to Westmead Hospital.