A terrified service station worker had a high-powered rifle pointed at them over the counter when two robbers burst into the Masterton store on Wednesday night.
Detective Senior Sergeant Barry Bysouth said two people entered the BP petrol station on Chapel St shortly after 9pm.
They were dressed in dark clothing and had their faces covered.
The pair threatened a petrol station employee, who was working alone at the time, with a firearm and demanded cash and cigarettes, Bysouth said.
They left the BP and headed towards Renall St and then possibly west towards Pownall St junction.