A manhunt is underway in south Auckland, after an armed hold up at a petrol station in Manurewa.

Police say two people entered the Caltex station on Great South Road just before midnight, brandishing a firearm and demanding cigarettes and money.

They fled in a silver Nissan Laurel driven by a third person .. but crashed only a short time later into a parked car on Mahia Road.

All three ran from the scene.

Detectives are appealing for witnesses to either the robbery or the crash to come forward.