The stabbing took place at a Countdown supermarket in central Dunedin on South Island in the afternoon.
One person has been taken into custody, authorities said.
Prime Minister Jacinda Ardern said the motivation behind the attack was not clear but that there was no indication it was a domestic terror event.
“At this stage, there’s nothing to suggest from the police’s perspective that this is what they would define as a domestic terror event,” she told reporters.
Incidents of mass violence are rare in New Zealand but the country saw the 2019 Christchurch shooting when a white supremacist killed more than 50 people at two mosques.
Police district commander Paul Basham described Monday’s incident as a “random attack”.
He also said it was “nothing short of heroic” that other shoppers had tried to stop the attacker, saying they had prevented more injuries.
Local media reports say the four injured are made up of both supermarket employees and customers. Witnesses also described chaotic scenes at the supermarket.
Source By: BBC