Prime Minister Jacinda Ardern has paid respects to the families and victims of the Christchurch massacre in a rousing speech in Parliament.

March 15, 2019, will be remembered as New Zealand's "darkest of days", Ardern said during a special Parliament gathering where only tributes were paid.

"For the families, it was more than that. It was the day that the simple act of prayer - of practising their Muslim faith and religion - led to the loss of their loved ones lives," she said.

"Those loved ones, were brothers, daughters, fathers and children. They were New Zealanders. They are us. And because they are us, we, as a nation, we mourn them."

The Prime Minister reflected on the impact the Friday mosque shooting - where 50 people were killed - has had on her, including taking on a role that she "never anticipated having, and hoped never to have".

That role has been to "voice the grief of a nation" - a role which Ardern has taken under her stride and been praised for around the globe.

An article in The Guardian described Ardern as "showing the world what real leadership is", saying she has shown "sympathy, love and integrity" in the wake of the attacks on two mosques in Christchurch.

"In this role, I wanted to speak directly to the families. We cannot know your grief, but we can walk with you at every stage," Ardern said in Parliament.

"We can, and we will, surround you with aroha, manaakitanga and all that makes us, us. Our hearts are heavy but our spirit is strong."

She went on to acknowledge some of the many acts of bravery from Friday, including the police officers who rammed the alleged gunman's vehicle from which he was still shooting.

"They pulled open his car door, when there were explosives inside, and pulled him out," the Prime Minister said.