New Zealand Prime Minister Jacinda Ardern vowed on Saturday to tighten counter-terrorism laws this month after a knife-wielding militant known to the authorities stabbed and wounded seven people in a supermarket.

Police shot dead the 32-year-old attacker, a Sri Lankan national who had been convicted and imprisoned for about three years before being released in July, moments after he launched his stabbing spree on Friday.

Ardern said earlier the man was inspired by the Islamic State group and was being monitored constantly but could not be kept in prison by law any longer.

“I am committing, that as soon as Parliament resumes, we will complete that work that means working to pass the law as soon as possible, and no later than by the end of this month,” Ardern told a news conference.

The Counter Terror Legislation Bill criminalises planning and preparation that might lead to a terror attack, closing what critics have said has been a loophole allowing plotters to stay free.

But Ardern said it would not be fair to assume that the tighter law would have made a difference in this case.

“This was a highly motivated individual who used a supermarket visit as a shield for an attack. That is an incredibly tough set of circumstances,” she said.

Ardern said the attacker came to the attention of the police in 2016 because of his support for a violent ideology inspired by Islamic State.

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.