Australian police and intelligence agencies have joined an investigation into the Christchurch mosque shootings after it was revealed an Australian man was in police custody.
Brenton Tarrant, originally from the northern NSW town of Grafton, was one of four people arrested over the shooting attacks at two mosques in the South Island city which killed at least 49 people.
Prime Minister Scott Morrison met with agency chiefs on Friday after what he described as the "vicious and callous, right-wing extremist attack" which has claimed multiple lives.
"I can confirm that the individual who was taken into custody, I have been advised, is an Australian-born citizen," he told reporters in Sydney.
"Obviously that element of the investigation Australian authorities are involved in and they will be proceeding with their investigation."
Mr Morrison said he was being kept abreast of developments in New Zealand, as federal and state police along with the Australian Security Intelligence Organisation investigated.
"I want to assure all Australians that the immediate responses that are required to ensure the security and safety of Australians have already been actioned," he said.
Australia's terrorism alert level has not been lifted.
Mr Morrison said he had heard nothing to suggest any Australians were affected by the shooting.
NSW police have offered assistance to their NZ counterparts, Premier Gladys Berejiklian confirmed on Friday.
Labor leader Bill Shorten said Australia and New Zealand are family.
"There is so much we still do not know about this senseless evil act of murder but it is chilling in its callous preparation, it is horrifying in the scale of death and injury," he said.
He also urged people not to watch or share the footage taken by the alleged shooter.
"Evil is never normal, evil is never part of daily life. We must do everything we can to unite and prevent this happening again."
Australian Associated Press