A woman was kicked unconscious during a rampage by a gang of youths in Melbourne's north-west on Saturday.

Police say the crime spree started in Mickleham just before 3am when three males got out of a dark blue car and approached a parked car in a Mount Ridley Road car park.

The woman told Channel Seven she was hit in the head when she tried to help a young man being threatened. Credit:Twitter: @7NewsMelbourne

The trio tried to force their way into the car but were thwarted and drove away.

Police say about half-an-hour later, the same group approached a 22-year-old man who was starting a shift at a Woolworths supermarket in Craigieburn.