Police are investigating the circumstances surrounding an armed robbery at a service station in Kogarah overnight.

About 12.25am (Tuesday 9 August 2016), a 21-year-old man was working behind the counter of a service station on the Princes Highway when a man approached the front glass door.

The attendant allowed the man entry and he approached the counter and asked for a packet of cigarettes. As the attendant turned to the cigarette cabinet the man produced a large knife and threatened him while demanding money from the till.

The attendant handed the man a sum of cash and he ran from the scene heading east along President Avenue.

Police were called and a crime scene was established while forensic investigators carried out further inquiries.

The man has been described to police as being aged in his mid 20’s, about 178cm tall with a skinny build and fair skin.

At the time of the offence he was wearing a red beanie, black hooded jacket with a hood pulled tight over his head with blue jeans and black joggers.