Police are investigating following an armed robbery on the Central Coast early this morning.

About 3.30am (Wednesday 8 July 2015), a man entered a service station on The Entrance Road, Erina, and threatened the male attendant with a knife, demanding cash.

The attendant handed over cash before the man ran from the store headed toward Erina Fair.

Police from Brisbane Water Local Area Command attended and a crime scene was established, which was examined by specialist forensic officers.

Officers conducted extensive patrols of the area; however, the man was not located.

Detectives would like to speak to anyone with information about the robbery to assist them with their investigation.