Police on the Kapiti coast north of Wellington are investigating a spate of attacks on residential and commercial properties.
Constable Vanessa Knyn says those responsible have targeted mainly homes in the town of Paraparaumu, firing objects such as marbles and stones at windows and causing considerable damage.
Ms Knyn says 30 such incidents have been reported since early last month.
She says the offenders appear to be using equipment to fire the projectiles at high speeds, and there are concerns someone will get hurt.
Police are appealing for anyone with information about the attacks to contact them.