Three teenagers have been arrested after they led police on a pursuit through Sydney’s north-west and injured an officer.

Around 10 o’clock last night police spotted a stolen Toyota travelling through Blacktown.

When one officer approached the vehicle the driver started the car and drove away, knocking the senior constable to the ground.

Officers initiated a pursuit with the help of the Aviation Support Unit but the driver then allegedly attempted to ram several police cars and the pursuit ended.

Polair continued to follow the car to Seven Hills where four people abandoned the car and ran into parkland.

With the assistance of the Police Dog Unit three people were arrested.

A 15, 17 and 18-year-old man were taken to Blacktown Police Station while officers continue to search for the fourth person.

The injured officer was taken to hospital with injuries to his forearm and grazes.

Image: Getty