Two dead after late-night police pursuit

Two males have been killed when a car rolled and caught fire during a police chase in Sydney, while another man has died in a separate fiery crash on NSW's mid north coast.

NSW Police launched a critical incident investigation into a crash, which happened just before 12.30am on Tuesday at Strathfield, in the city's inner west.

Highway patrol officers were patrolling Centenary Drive in Sydney, when they attempted to stop a silver Audi which was allegedly speeding.

Police said the driver failed to stop the car as directed and they started a pursuit, but a short time later the car crashed on to its roof on the entry ramp to the M4 motorway and caught on fire.

The occupants couldn't be freed despite attempts by police and bystanders. The pair are yet to be formally identified.

In Chinderah, emergency services were called to the Pacific Highway just after midnight with reports of a Mitsubishi sedan leaving the road and crashing into the back of a parked B-double truck before bursting into flames.

A man's body was discovered inside the car after the fire was put out by Fire and Rescue NSW.

The man is yet to be formally identified.

NSW Police commander Adam Whyte said the vehicle in Sydney travelled through a guard railing into nearby bush and dropped off the side onto the slip road, landing on its roof.

"The on-ramp goes into a protected slip road to enter the M4 for westbound traffic and the vehicle collided with the (safety barrier) at the entry to the sweeping bend into the on-ramp," Commander Whyte said.

He said these sort of incidents where people are harmed, injured or killed were unnecessary.

"If you are speeding and you get detected by police speeding, it is far easier for you to stop and basically accept the consequences of your actions," Commander Whyte said.

Police said their investigation into the incident would be subject to independent review.

Motorists were faced with heavy traffic, with several lanes of the M4 motorway closed, along with feeder roads.

Police are investigating and a report will be prepared for the coroner.