WELLINGTON: New Zealand supermarket group Countdown said on Saturday it has removed knives and scissors from its shelves, a day after a man the authorities called an Islamist extremist stabbed six people in one of the company's stores.

"Last night, we made the decision to temporarily remove all knives and scissors from our shelves while we consider whether we should continue to sell them," said Kiri Hannifin, Countdown’s general manager for safety.

"We want all of our team to feel safe when they come to work, especially considering the events of yesterday," she said in a media statement.

Other supermarket chains had also removed sharp knives from sale, local media reported.

Police shot dead the attacker, a Sri Lankan national who cannot be named due to court suppression orders. Prime Minister Jacinda Ardern said the man was inspired by the Islamic State militant group and had been under constant police surveillance.

Police were following the man when he went into the Countdown supermarket in New Lynn mall in Auckland. They said they had thought he had gone in to do some shopping, but he picked up a knife from a display and started stabbing people.

Police said they shot him within a minute of the start of the attack. Three of the six victims are in critical condition.

Ardern said the attacker had been under surveillance since 2016 because of his support for a violent ideology inspired by the Islamic State. By law the man could not be kept in prison, so he was being constantly monitored instead.

The government has sought an urgent lifting of the suppression orders so more details on the person could be made public. Ardern is expected to address the media at 0200 GMT.