A 35-year-old man was hit after running onto William Street in Darlinghurst at the same time officers were travelling under lights and sirens to the incident, police said.

He collided with the police car and was assisted at the scene by officers before paramedics arrived.

The man was taken to St Vincent’s Hospital in a serious condition.

His condition was later upgraded to stable.

The driver of the police car, a constable from Kings Cross Police Area Command, was also treated at the scene for shock.

NSW Police Superintendent Jill Walters said the urgency in which the police car was travelling was “justified”.

Walters said the victim was walking across an area of a main road which did not have any traffic lights.

His family live overseas and police are attempting to contact relatives, Walters said.

She said the officer behind the wheel was “understandably [in] immediate shock” and that his welfare remains a priority for police.

Police are now investigating the circumstances of the crash and an internal investigation will take place.

Anyone with information or who has dashcam footage of the area around the time of the incident is urged to come forward and contact police or Crime Stoppers on 1800 333 000.