Prime Minister Jacinda Ardern has confirmed 40 people have died in the Christchurch shooting, and fiercely condemned those involved.
"You may have chosen us but we utterly reject and condemn you," the Prime Minister said during a Friday night press conference in Parliament.
She said it's believed 40 people have lost their lives in Christchurch, 10 who died at the Linwood mosque, three outside that mosque, and a further 30 at the Dean Ave mosque.
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The shooting could "only be described as a terrorist attack", Ardern said, adding that it appeared to have been "well-planned", and that two explosive devices were found attached to vehicles.
The Prime Minister said she would describe the four people taken into custody - three men, one of whom is confirmed as Australian, and one woman - as having "extremist views".
While there is no reason to believe there are other suspects, Ardern said the Government is "not assuming at this stage" that there aren't others involved.
Therefore, New Zealand's threat level has been lifted from 'low' to 'high', whereby extra security has been put in places such airports and other public areas. It's the first time New Zealand's threat level has been lifted to 'high'.
"Police are working hard to ensure people can move around the city safely," she said, adding that her "thoughts and prayers" are with those directly affected.
The Prime Minister expressed sincere regret that the people killed in the shooting - who she said were potentially immigrants living in New Zealand - were targeted by a hateful tirade.
"[New Zealand] was a place that many came to for its safety - a place where they were free to practice their culture and religion," she said.
New Zealand represents "diversity, kindness, compassion", the Prime Minister said. "For many this may not have been the place they were born."
She said the individuals involved in the incident were not on New Zealand's watch-list, but would not offer more details about them at this stage.
It's understood 48 patients, including children, are being treated in Christchurch Hospital for gunshot wounds. Twelve operating theatres are currently in use with some patients needing multiple surgeries.
Canterbury District Health Board told Newshub the injuries range from minor to critical.
The Prime Minister's Office confirmed earlier on Friday that the National Security System has been initiated, and that Ardern would be meeting with the heads of relevant agencies for a meeting at the Parliament's bunker.
It was understood members of the Official Committee for Domestic and External Security Coordination (ODESC) arrived at the Police National Headquarters on Friday afternoon, ahead of Ardern's arrival in Wellington from Taranaki.
New Zealand Security Intelligence Service (SIS) boss Rebecca Kitteridge was seen heading to the ODESC meeting, along with the heads of the Ministry of Foreign Affairs and Trade (MFTA), Civil Defence, and the Department of the Prime Minister and Cabinet (DPMC).
"This is one of New Zealand's darkest days," Ardern told media earlier on Friday, adding that her thoughts were "with those in Christchurch".
"This is an act that has absolutely no place in New Zealand - this is not who we are," the Prime Minister said.
"They have no place in New Zealand society."