Police are investigating a number of armed robberies that occurred across Sydney overnight.

The first incident was an attempted armed robbery that occurred shortly after 8pm (Monday 19 October 2015), where a man armed with a pistol entered a supermarket on Bonnyrigg Avenue.

He threatened a staff member and demanded cigarettes but was unsuccessful and left the store empty handed.

The next report came at 11pm (Monday 19 October 2015), at a service station on the Hume Highway, Lansvale, where a man, described as having a large build and armed with a knife entered the store.

He threatened the console operator before stealing an amount of cash and cigarettes.

A short time later, about 11.40pm, police believe the same man responsible for the Lansvale robbery then entered a service station on Victoria Street, Smithfield, armed with a knife.

He threatened the employee before running from the store with an amount of cash and cigarettes.

The fourth incident occurred at a service station on Dunheved Road, Werrington about 12.15am. This robbery involved two men, one described as Pacific Islander/Maori in appearance with a large build, and the second man as having a thin build, entered the store armed with a firearm.

They threatened the employee before running from the scene with cash and cigarettes.

No one was injured during the robberies, and police from Fairfield, Cabramatta and St Marys commands are now conducting a full investigation and would like to speak with anyone who may have information that can assist.