Police are investigating an armed robbery at a Mayfield service station.

A man entered the 7-11 on Maitland Road at about 5.00pm on Sunday and threatened the console operator with a knife.

Police say the man was handed an amount of cash before leaving the store.

He’s described as being in his 40’s, about 178 centimetres tall with a stocky build.

He was wearing a light coloured jumper, blue jeans and a baseball cap and had his face covered.

No-one was injured during the incident.