Police said an unknown man entered the Nelson Bay Road service station about 11.15pm on Monday and threatened a 59-year-old female employee with what is believed to have been a knife.

He took a sum of cash and cigarettes before fleeing the scene.

Officers from Port Stephens-Hunter Police District were called a short time later and established a crime scene.

The man is described as being of Caucasian appearance, aged between 25-30, about 180cm tall, with a thin build.

He was last seen wearing a tan hooded jacket, dark pants, work boots and a dark and light coloured beanie.

Anyone with information is urged to contact Raymond Terrace Police Station on (02) 4983 7599 or Crime Stoppers on 1800 333 000.