New Zealand's Prime Minister Jacinda Ardern has vowed never to say the name of the Christchurch mosque gunman.

"He sought many things from his act of terror, but one was notoriety - that is why you will never hear me mention his name," Ms. Ardern said in an emotional address at New Zealand's parliament.

Last Friday's shootings at two mosques left 50 people dead and dozens wounded.

Australian Brenton Tarrant, 28, a self-described white supremacist, has been charged with murder.

Ms. Ardern said: "I implore you, speak the names of those who were lost rather than the name of the man who took them. He is a terrorist. He is a criminal. He is an extremist. But he will, when I speak, be nameless."

In a special meeting of parliament on Tuesday, Ms. Ardern used the Arabic greeting "Al-Salaam Alaikum", which in English means "peace be upon you".

The prime minister called on social media platforms to do more to combat terror, after the gunman in Christchurch live-streamed his attack on Facebook.

"We cannot simply sit back and accept that these platforms just exist and that what is said on them is not the responsibility of the place where they are published," she said. "They are the publisher. Not just the postman. There cannot be a case of all profit no responsibility."

Facebook said on Tuesday that the video was viewed fewer than 200 times during the live broadcast, and about 4,000 times in total before it was removed. The social media company said it removed more than 1.5 million copies of the video in the first 24 hours after the incident, 1.2 million of which were blocked while being uploaded.