Scott Morrison confirms Australian taken into custody after 'vicious, murderous' terrorist attack

An Australian citizen has been detained as the key suspect in a deadly terrorist assault Prime Minister Scott Morrison has condemned as a "vicious, murderous attack" on people of faith.

Mr Morrison revealed an investigation has been launched after security agencies told him the man believed to be behind the storming of mosques in the New Zealand city of Christchurch was an Australian-born citizen.

"We are outraged and we stand here and condemn absolutely the attack that occurred today by an extremist, right-wing violent terrorist who has taken the lives, stolen lives, in a vicious, murderous attack that has claimed so many New Zealanders," Mr Morrison said from Kirribilli House in Sydney.

More than 40 people inside and outside the Al Noor Mosque in central Christchurch and the Linwood Mosque in the city's outer suburbs have been killed. New Zealand police have taken four people into custody.

Mr Morrison said he had no information to suggest any Australians had been killed but noted it was "very early on" and the situation was unfolding.

A manifesto posted to social media by a person claiming to be named Brenton Tarrant notes he was born in Australia and it is believed he spent time living in Grafton, in northern NSW.

"These people don't deserve names," Mr Morrison later said. "Names imply some sort of humanity and I struggle to see how anyone who would engage in this sort of hate and violence is human. He doesn't deserve a name."

The Prime Minister said he was not known to Australian authorities.

Mr Morrison has been briefed on the manifesto document: "It is the work of hate," the Prime Minister said. "I've got no other way to describe it.

"That sort of hateful thinking has just reaped murder and misery on a peaceful peope just going about their practice of faith on a Friday. It's disgusting."

Prime Minister Scott Morrison speaks to the media in Sydney.Credit: AAP

Mr Morrison has met senior national security officials, and while noting authorities had "already put in place all the necessary responses and precautions" he did not go into details.

"This attack reminds us of the evil that is ever-present and would seek to strike out at any time and I particularly want to convey my heartfelt sympathies not only to all New Zealand people, but particularly my sincere prayers and thoughts for those New Zealanders and indeed Australians of Islamic faith who have been the subject of this callous right-wing extremist attack," he said.

Opposition Leader Bill Shorten declared the assault a "senseless, evil act of murder".

"It is chilling in its callous preparation, it is horrifying in the scale of death and injury," he said.

"This was an attack on a mosque. It could have been a church. It could have been a synagogue. This is an attack on worshippers practising their faith innocently. And attack on any religion is an affront on all religions. It is an affront on our common humanity.

"I particularly feel for the Islamic Australian community who must be feeling very, very concerned and upset and also for all the parents who have to try to explain this to their children tonight."

Mr Shorten urged Australians to not watch or share footage of the attack filmed by the gunmen.

"This is not normal, do not make this violence normal. Evil is never normal. Evil is never part of daily life."

The Department of Foreign Affairs is working with New Zealand authorities to determine whether any Australians have been killed in the attack."

"Australians concerned for the welfare of family and friends in the area should attempt to contact them directly," a spokeswoman said.