The region's deputy mayor, Kelly Stratford, requested privacy for the small Moerewa community as they dealt with the tragedy.
The woman had been hanging out washing on Thursday afternoon when the dog came onto her property in Otira Rd and attacked her.
The dog was reportedly shot by a neighbour before police arrived.
Stratford said its body was removed from the scene by Animal Control.
A family member in Moerewa told RNZ his aunt had been killed and distraught family members gathered outside the house.
Police were alerted to the attack about 4.40pm and arrived to find the woman's body, acting Senior Sergeant James Calvert said.
A scene examination was being carried out.
Police confirmed the dog had been killed and there was no ongoing risk to the public in relation to the attacks.
St John said two people suffered moderate injuries after also being attacked by the dog.
One was taken to Bay of Islands Hospital in Kawakawa.
Earlier, it was reported two people had been taken to hospital.
The death has been referred to the coroner.
Last year, Northland man Neville Thomson was attacked by dogs he was temporarily looking after. The attack happened on the 69-year-old's property in Pānguru.
