New Zealand Prime Minister Jacinda Ardern said her office received a "manifesto" from the gunman suspected of killing 50 people in two Christchurch mosques minutes before Friday's attack.

"I was one of more than 30 recipients of the manifesto that was mailed out nine minutes before the attack took place," Ardern told reporters on Sunday.

"It did not include a location, it did not include specific details," she said, adding that it was sent to security services within two minutes of receipt. Ardern said she had read "elements" of the lengthy, meandering and conspiracy-filled far-right "manifesto".

"The fact that there was an ideological manifesto with extreme views attached to this attack, of course, that is deeply disturbing," she said.