Motorcyclist dead after being struck by police car in Sydney

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Shortly before 2am, the motorcycle was heading east along the M4 near Church Street, Parramatta.

It collided with a white sedan, and the rider was thrown onto the road.

A motorcyclist is dead after being struck by a police care on the M4 near Parramatta.

A marked police car then hit the rider.

Police and paramedics provided emergency CPR and the man was taken to hospital but could not be revived.

He is yet to be formally identified.

Police say the police car was not pursuing the motorcycle.

The sedan driver and a senior constable, both men, were also taken to hospital for mandatory testing.

A critical incident investigation into the crash is underway.

NSW Police said the police car was not on urgent duty and did not have its lights or sirens activated at the time.

The M4 remains closed with traffic backed up for 12km and more.

"There had been no interaction with and no pursuit of the motorcyclist or any other vehicle," police said in a release.

"Initial information is the officers were returning to the station when the incident occurred."

All M4 citybound lanes are closed between the Cumberland Highway and Burnett Street, with traffic already queued over 12km back.

Drivers are urged to avoid the area, as police investigators are likely to remain on the scene for some time.

Traffic is also heavy on the diversion route of the Great Western Highway, so citybound motorists should consider using an alternative route including using the M7 to the M2 or the M5.

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