Up to seven men armed with baseball bats, hammers and a knife smashed their way into three service stations in Melbourne's north-west over the weekend, fleeing with cash, cigarettes and a car.

In the first incident, seven men targeted a service station on the Melton Highway in Hillside just after 3am on Saturday.

The group tried to break into a cigarette cabinet but failed. Instead, they stole the service station attendant's car and escaped.

The attendant, who was in the cool room at the time, was uninjured.