New Zealand authorities say they shot and killed a violent extremist after he entered a supermarket and stabbed and injured six shoppers.

Prime Minister Jacinda Ardern described Friday's incident as a terror attack. She said the man was a Sri Lankan national who was inspired by the Islamic State group.

She said he was well known to the nation's security agencies and was being monitored around the clock.

"What happened today was despicable. It was hateful; it was wrong," Ardern said in a news conference, according to the BBC. "It was carried out by an individual, not a faith."

Ardern said that because the man was under constant monitoring, a police surveillance team and a special tactics group were able to shoot and kill him within 60 seconds of the attack starting.

The prime minister added that despite the police presence, the suspect had not been detained prior because he had not committed a crime.

"Had he done something that would have allowed us to put him into prison, he would have been in prison," Ardern said, according to NPR.

She said that three of those who had been stabbed were seriously injured. Another was in serious condition, while two more were in moderate condition, according to NPR.