A counter-terrorism expert is warning that New Zealand "needs to wake up and be aware" a terrorist attack will happen again.
Massey University teaching fellow Dr John Battersby told Breakfast that while Government can introduce strict measures to prevent attacks, there's no way to stop them altogether.
It comes after Prime Minister Jacinda Ardern confirmed authorities had exhausted most options trying to deport the terrorist who injured seven people in Friday's attack at the Countdown supermarket in LynnMall, Auckland.
"Prevention would have been ideal, but we don't live in an ideal world. There isn't a security apparatus in the world that has managed to completely stop terrorist attacks," Battersby said.
"'Im afraid I do have to say to New Zealand, we need to wake up and be aware this is going to happen again."
"We'll possibly stop and mitigate a number of them, but we just can't say it won't happen again".
He noted that police and the NZSIS had done as much as was legally "possible" by monitoring the terrorist. The terrorist was shot dead by police soon after launching the attack.
"They've got to try and maintain that critical balance between keeping someone in sight and trying to be in a position to intercept and mitigate the risk if they do something," Battersby said.
"The most we can expect from our security agency is that they get on something, and if they do, they manage to mitigate it as much as possible."
He acknowledged that New Zealand tends to act slowly on counter-terrorism laws but that changes would need to give authorities more power controlling risks.
"This is a dreadful sort of draconian place to go, it's going to be a breach of our Bill of Rights, but we must weigh up society's want to be safe against the rights of a prospective terrorist.
"We need to look at powers that are more restrictive or powers that would allow our security agencies to introduce more control of individuals where there is a high probability of an attack."
Battersby added that New Zealand needed to shift from prosecution-focused model for a dealing with terrorism to a preemptive model.
"We need to be able to prosecute someone for an offence they're committed or are planning and preparing one."
New Zealand's terrorism alert level is at medium, where it had been before Friday's terrorist attack.