New Zealand Prime Minister Jacinda Ardern vowed to quickly tighten counter-terrorism laws after a known ISIS sympathiser went on a stabbing spree in an Auckland 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 attack on Friday. Ms Ardern said five of the seven people injured remained in on hospital on Saturday, three of them in a critical condition. Ms Ardern said the man was inspired by ISIS 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," Ms Ardern told a news conference on Saturday. 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 the prime minister 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. She said the attacker came to the attention of the police in 2016 because of his support for a violent ideology inspired by ISIS. Police were following the man when he went into the Countdown supermarket in New Lynn mall in Auckland. They said they thought he had gone in to do some shopping but he picked up a knife from a display and started stabbing people. Police commissioner Andrew Coster said there had been nothing unusual about the man's actions in the lead up to the attack. Mr Coster said the police kept their distance because he had a "high level of paranoia" around surveillance, and it took more than two minutes to reach the man and shoot him after he started his frenzied stabbing spree. "We have had no legal grounds to detain this subject. Monitoring his actions has been entirely dependent on the surveillance teams being able to maintain their cover as they watched him over an extended period," he said. Ms Ardern said the man was not known to have held any extreme views when he arrived in New Zealand in 2011 on a student visa. He came to the attention of police after he expressed sympathy on Facebook for militant attacks, violent war-related videos and comments advocating violent extremism. In May 2017, he was arrested at Auckland's airport. Authorities suspected he was travelling to Syria. He was charged after restricted publications and a hunting knife were discovered at his house but was released on bail. In August 2018, he again bought a knife and was arrested and jailed. He was released into the community in July this year when surveillance began, Ms Ardern said. The prime minister was briefed on the case in late July and again in late August and officials, including the commissioner of police, raised the possibility of expediting the amendment to the counter-terrorism legislation. Ms Ardern said she wanted to explain why the attacker had not been deported but could not because to do so would violate court suppression orders, which also prevented her from identifying him, she said. Although the court ruling was lifted by a judge on Friday, his family have been given at least 24 hours to appeal "the release of certain information", Ms Ardern said. "So while I can provide details concerning the individual's criminal history, there are issues relating to his immigration status, and actions taken by Immigration New Zealand in particular, which I cannot share just yet." She said she had no intention of naming him anyway. "No terrorist, whether alive or deceased, deserves their name to be shared for the infamy they were seeking," she said. New Zealand supermarket group Countdown said on Saturday it had removed knives and scissors from its shelves, while it considers whether it would continue to sell them. "We want all of our team to feel safe when they come to work," said Kiri Hannifin, Countdown’s general manager for safety. Other supermarket chains had also removed sharp knives from their shelves, media reported.