Police are appealing for help following an armed robbery in Sydney’s south-west.

Just before 10pm on Monday 29 January 2018, a man entered a service station on Harold Road, Macquarie Fields, armed with a knife.

Police have been told the man threatened the store employee before demanding cash, which the employee handed over, before activating the alarm.

The man fled the scene and ran south along Harold Street.

Officers attached to Campbelltown Local Area Command established a crime scene and commenced an investigation.

Following inquiries, police would like to speak to a man who might be able to assist with the investigation.

He is described as being of Pacific Islander/Maori appearance, 170-175cm tall, aged between 15-20, with a medium to solid build, dark complexion and dark hair. He was last seen wearing black t-shirt with white logo, tan shorts, white socks, black shoes and a white shirt covering his face with sunglasses.

Inquiries are continuing.