A female robber held up a dairy, took cash, assaulted the owner then fled the scene on a bicycle.
The incident happened about 6.30pm this evening in Palmerston North and left a man needing hospital treatment.
The female offender arrived at the Westend Store on the corner of Botanical Rd and College St on a bicycle, police said.
"The offender has entered the store and threatened the female store owner and demanded money," police said.
"After taking cash the offender has fled the store and been confronted by a male store owner on the street outside the store. The male has been assaulted and has suffered injuries that require hospital treatment.
"After assaulting the male store owner the offender has fled the scene by bike down College Street heading towards the town centre."
The woman is aged 25-30 years, of medium to large build and 160cm in height with black hair. She was wearing a dark-coloured sweatshirt and light-coloured pants.
Police want to hear from anyone who witnessed the incident or saw any suspicious activity in the area of Westend Store this evening.
"The store is on a busy intersection and it is likely someone would have seen the offender approaching or leaving the scene or the assault outside the store," said Detective Sergeant Dave Thompson.
"The offender would have been in an agitated state after the robbery and would have been on edge. If you know who this person is or saw anything in relation to the robbery please call police."
Anyone with information can call Palmerston North Police on 06 351 3600. Information can also be shared anonymously via Crimestoppers on 0800 555 111.