Five teens critical after Sydney car crash

Five teenagers are fighting for life after a high-speed, single-vehicle, fiery crash on Sydney's lower north shore, as police declare a critical incident investigation.

Police say they terminated a pursuit of the Holden Commodore, which was allegedly being driven by a 16-year-old girl, shortly before it left the road, struck a tree and burst into flames on Sunday, in suburban Cammeray.

Commander of the North Shore Police Area Command, Detective Superintendent Paul Devaney says prior to the crash, officers had been called to reports of a fight in nearby Wollstonecraft, allegedly involving the teens.

"Police were called to a report that a male had been assaulted by four other persons, and obviously that vehicle was connected to that incident," he told reporters on Monday

"A 17-year-old male was assaulted. We believe he had organised to meet the occupants of (the car) but the reason for that meeting is yet to be determined."

The car which belonged to a 18-year-old male passenger, failed to stop for police who gave chase before twice ending the pursuit for safety reasons.

"This was a horrific incident that is likely to have lifelong consequences for all involved," Det Supt Devaney said.

The actions of police who dragged the injured teens from the burning wreck were "nothing short of heroic", he said.

"If they didn't remove those occupants from the vehicle I'd think we had a fatality for sure."

A 16-year-old girl, who was allegedly driving the sedan, has head and spinal injuries, while a second 16-year-old girl has head and facial injuries.

The back-seat passengers included an 18-year-old man, who has head and chest injuries, and two male youths, both 17. They are suffering spinal injuries, with one also being treated for abdominal injuries.

All are reported to be in a critical condition, some in induced comas, in Royal North Shore Hospital.

A critical incident team from Blue Mountains Police Area Command is now investigating the circumstances surrounding the incident under Strike Force Mulvany.

The investigation will be subject to independent review.

Police are appealing for anyone with dashcam vision or who witnessed the crash to come forward.