A critical incident investigation has been launched by NSW Police after the motorcyclist was severely injured soon after passing a police vehicle in suburban Wagga on Tuesday afternoon.

A man aged in his 20s sustained severe leg trauma when he collided with a Toyota sedan on Red Hill Road just after 4.30pm. 

The motorcyclist had just moments before been observed allegedly travelling over the speed limit by a passing police car, NSW Police said in a statement.

The officers then turned the vehicle around in order to pull over the bike.

Soon after, the motorcycle collided with a car 500 metres east of the intersection of Red Hill Road and the Olympic Highway.

Officers administered immediate first aid to the rider, police said, before paramedics worked further when they arrived.

A spokeswoman for Ambulance NSW confirmed paramedics responded to Red Hill Road at Ashmont around 4.30pm.

Upon arrival they found a man aged in his 20s with “a critical leg injury” and he, along with the driver of the sedan, was taken to Wagga Rural Referral Hospital.

The motorcyclist was in a serous condition, the spokeswoman said, and the SouthCare helicopter was tasked to the city.

NSW Ambulance could not confirm early reports that indicated the man’s leg was severed in the crash.

The sedan driver, a man aged in his 50s, was treated for minor injures and will undergo mandatory testing.

Red Hill Road was closed between Yentoo Drive and the Olympic Highway as investigations began and on Tuesday evening a critical incident team was formed from an independent local area command from within the Southern Region.

It will investigate all circumstances surrounding the incident and police are appealing for witnesses to come forward by calling Crime Stoppers on 1800 333 000.