A manhunt is under way after a man was shot in the leg outside a shopping centre in Melbourne's north.

The victim was shot in the car park outside an Officeworks store on Sydney Road in Campbellfield just after 3.30pm on Monday.

"Police have been told a man armed with a firearm approached the victim in the car park, before shooting him a number of times in the leg," a police spokeswoman said.

"The offender then fled in what is believed to be a red Holden Commodore and was seen heading towards the Dallas area."