A 28-year-old man will appear in court charged with murder after the massacre of 49 people in two mosques in New Zealand.
Police have declined to confirm if the man is former NSW personal trainer Brenton Tarrant, one of four people arrested over the shootings that began as hundreds of worshippers gathered for prayers in the South Island city of Christchurch on Friday.
Officials say 41 people were killed at the Masjid Al Noor mosque on Deans Avenue, seven in the Linwood Masjid six kilometres away, and another died in hospital.
A further 48, children and adults, were being treated for gunshot wounds overnight, while hundreds of family members waiting for news in Christchurch Hospital.
Calling it one of the darkest day's in her nation's history Prime Minister Jacinda said the well-planned attacked - the worst shooting in the country's history - had to be deemed terrorism.
Army personnel were also called in to dismantle explosive devices found in a stopped car and police were in the evening searching a house in Dunedin, 360 kilometres away, clearing nearby homes for safety.
None of the three men and one woman arrested, three directly tied to the attack, were on the watchlists of New Zealand or Australian security agencies and their alleged movements and involvements during the shootings were still unclear.
Only one had been charged by Friday night and would appear in the Christchurch District Court on Saturday, according to police
Reports of gunfire first came at about 1.40pm on Friday, armed officers descending on the Al Noor mosque near Hagley Oval, clearing the public from the area and sending the city into lockdown.
Notification of a shooting at the second mosque followed, before video emerged of police ramming a car and pulling out the occupant.
Witnesses described bloody scenes and bodies falling to the ground as worshippers ran for doors and a shooter moved from room to room for around 20 minutes.
One told AAP he hid under a bench and pretended to stop breathing as the gunman reloaoded seven times.
'He went to all the different [rooms] and he shot everyone,' he said.
Tarrant, 28, grew up in Grafton in NSW and stated in a rambling 74-page 'manifesto' he had spent years planning an attack in vengeance for deaths in Europe, before deciding on Christchurch three months ago.
A post on a message board website linked to Tarrant also said the attack 'against the invaders' would be live-streamed on social media.
A 17-minute video taken from a helmet camera showed a shooter in his car, arming himself, getting out of the vehicle and entering the mosque where he started shooting appeared online.
Authorities and telecommunications companies were scrambling to take it down on Friday.
While New Zealand's threat rating was raised to high for the first time on Friday, Ardern refused to accept it would change the character of the country.
'We were not chosen for this act of violence because we condone racism, because we are an enclave for extremism,' she said.
'We were chosen for the very fact that we are none of those things. Because we represent diversity, kindness, compassion. A home for those who share our values. Refuge for those who need it.
'And those values will not and cannot be shaken by this attack.'