Police are appealing for information following an armed robbery at a Baulkham Hills service station overnight.

About 9.20pm (Friday 4 March 2016), officers attached to The Hills Local Area Command were called to the service station on Seven Hills Road after reports of a robbery.

Police have been told a man entered the premises and threatened the attendant with a firearm while demanding cash.

The man has been described as being about 175-185cm tall, of a medium build, and was last seen wearing a black jumper, dark-coloured pants and a balaclava.

He fled the scene a short time later with an amount of cash in a black plastic bag.

No one was injured during the incident.

Local police, with assistance from the Dog Unit and PolAir, conducted an extensive search of the surrounding area; however, the man was not found.

A crime scene was established at the location and examined by detectives and forensic specialists.

Investigations into the matter are continuing and anyone with information that could assist police is urged to come forward.