A manhunt's under way after two violent robberies in Hamilton on Tuesday night - including a member of the public being stabbed with a screw driver

Police say six offenders, armed with a hockey stick, machete and screw driver, simultaneously invaded a liquor store and dairy at Hillcrest shopping centre near seven pm.

The dairy owner was punched several times and a person who helped the liquor store owner was stabbed as the robbers fled.

Acting Detective Sergeant Simon Moore says it's imperative to identify such serious offenders as soon as possible.

Police are looking for two stolen vehicles, a white Mazda Familia wagon and a white-Honda Civic.