A 55-year-old woman was working in the College Avenue shop when she went into a rear office about 9.15pm.

When she returned to the front, she was confronted by a man armed with a knife, who demanded money.

The man left the store a short time later, taking cash, and was seen getting into the passenger seat of a small red hatchback.

The car, which police say was similar to a Kia model and driven by another man, was last seen travelling north along College Avenue.

The woman was uninjured during the incident.

Lake Illawarra police were called and officers would like to speak to a man who may be able to assist with their inquiries.

The man was described as being of medium build, about 183 centimetres tall, and was wearing a grey jumper and denim jeans.

Meanwhile Lake Illawarra Police are also investigating an armed hold-up of the Metropolitan petrol station in Shellharbour Road at 5.30 on Monday morning.

A woman threatened the attendant with a syringe before escaping with a sum of money.

At this stage it is not known if the two hold-ups are related.

Anyone with information is urged to contact police via Crime Stoppers on 1800 333 000.