A police woman in west Auckland has been knocked out in an assault while she was trying to arrest a man.

She's been admitted to North Shore Hospital after the attack last night, at the Ranui Railway Station.

Inspector Ben Offner says the officer and her partner were in pursuit of a stolen Subaru station wagon at about 10:30pm

"After five minutes of the pursuit the driver of that vehicle drove to the side of the road, stopped and the occupants tried to escape."

He says the officers tried to arrest the fleeing occupants.

"One of the police officers was attacked by the driver of the stolen Subaru and punched in the face a number of times and knocked unconscious by one of those punches."

The four offenders ran away through adjacent properties

Inspector Offner says staff get into confrontation situations all the time, but it's not often they get attacked to the extent of injury.

An 18-year-old is facing charges of aggravated assault and is due to appear in the Waitakere District Court today.

Two others were arrested at the scene after trying to flee from the officers.

One remains on the run.

Photo: NZ Herald