Key Points:

A police chase has ended with three people being taken to hospital, two in a life threatening condition.

The chase began at about 11.30am in Mt Eden when police tried to pull over a car with the wrong number plates on it. The car did not stop, said Auckland police spokeswoman Noreen Hegarty.

Inspector Willie Taylor said the car made it on to the South Western Expressway and reached speeds of up to 120km/h.

Police cars pulled back to 1km behind the car while the police helicopter Eagle followed, Mr Taylor said.

The car hit heavy traffic on Roscommon Road, near the airport, and drove down the median grass strip before spinning out of control and colliding with oncoming traffic, he said.

The accident happened between the intersections of Hautu Road and Kiwi Tamaki Road.

Mr Taylor said two people in the chased car were thrown from the car during the crash while the driver fled.

Ms Hegarty said the driver then tried to carjack another vehicle but was caught by police.

The driver who was hit by the chased car has a broken leg and sternum while both of the passengers in the chased car have life threatening injuries, Mr Taylor said.

"The manner of the driving was erratic," he said.

Mr Taylor said he has been told by air support that the police cars involved in the chase were "some distance back and not visible" to the driver trying to get away.

Inspector Keith Brady told reporters at the scene that the matter will be referred to the Police Complaints Authority because of the injuries caused by the crash.

Mr Brady said the police will be reviewing the chase as well.