A speed camera and the car carrying it have been stolen from the side of a road in north-west Melbourne.

The incident occurred on the Melton Highway at Sydenham about 8.30pm yesterday.

A speed camera operator was loading camera equipment into a Toyota RAV-4 four-wheel drive parked on the side of the road when a man approached and began talking to the operator, a Victoria Police spokeswoman said.

While the operator was at the back of the car, the man got behind the wheel and drove away, she said.

He was described as being of southern European appearance, about 25 years old and 1.7m tall, with a medium build, tanned complexion and short, black hair.

He wore blue denim jeans and a dark jacket.