Police are searching for the driver and passenger of a vehicle involved in a number of incidents that began in Springvale around 1.30pm.
Police observed a Honda on the Princes Highway in Springvale driving erratically, before the vehicle took off at speed.
The vehicle was followed through the south-eastern suburbs by the Airwing before the occupants dumped the Honda and carjacked three people.
The first was at the intersection of Parkers Road and Nepean Highway in Parkdale, the second car was stolen on Clayton Road in Clayton South and the third car was stolen on Boundary Road in Dingley.
The stolen vehicles driven by the offenders also collided with numerous civilian and police vehicles.
No one was seriously injured during the carjackings and collisions.
The males carjacked a fourth vehicle in the vicinity of Hoddle Street in Richmond and travelled city bound.
The vehicle and two occupants are yet to be located at this stage and the investigation is ongoing.
The vehicle is described as a silver 2009 Ford Falcon station wagon with registration XBX545.
Anyone with information or dashcam footage is urged to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au
