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," Ms 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.

Australian Brenton Tarrant, 28, a suspected white supremacist, was charged with murder on Saturday. Tarrant was remanded without a plea and is due back in court on April 5 where police said he was likely to face more charges.

Ms Ardern said she had read "elements" of the lengthy, meandering and conspiracy-filled far-right "manifesto".