A man is in custody after an armed robbery and pursuit in Sydney’s south-west overnight.

About 2.30am (Wednesday 10 January 2018), a man attended a service station on Hoxton Park Road at Lurnea, armed with a firearm.

The man approached the night service window and allegedly threatened an employee, demanding money before smashing a window and stealing cash from the register.

The man fled into a waiting vehicle, being driven by another man.

Officers from Liverpool Local Area Command attended and established a crime scene.

A stolen Kia Cerato was seen driving past on Hoxton Park Road.

Police followed the vehicle before a pursuit was initiated.

The vehicle mounted the kerb on Powderdrill Road, before two men were seen running off.

With the assistance of the Police Dog Unit, a 26-year-old man was arrested.

The second man was not located.

The man was taken to Liverpool Police Station before being transferred to Liverpool Hospital for treatment where he remains under police guard.

The employee was not physically injured during the robbery.