Woman on run after Sydney carjacking

A woman is on the run after allegedly carjacking a man's car after assaulting him in Sydney's west.

Police say a 46-year-old man was driving along The Horsley Drive in Fairfield West at about 11.30pm when he was flagged down by a female who appeared injured on the side of the road.

She asked the man to take her to hospital, but when they arrived at Fairfield Hospital, the woman refused to get out of the car and demanded the man take her back to the centre of Fairfield.

The woman then allegedly assaulted the man, and stole the man's car, a blue Toyota Avalon.

The man suffered minor injuries .

Police are looking for a woman who is described as being of slim build, about 40-years-old, tall, and may have a visible head injury.