New Zealand and France announced a joint effort Wednesday to bring countries and tech companies together in an attempt to end the ability of social media to organise and promote terrorism and extreme violence.

Ardern said the March 15 terrorist attacks on two mosques in Christchurch, in which 50 Muslim worshippers were killed, saw social media used "in an unprecedented way as a tool to promote an act of terrorism and hate".

The mosque attacks were live-streamed on the Internet and showed distressing footage of the gunman him firing indiscriminately at men, women and children.

Nearly six weeks after the massacre, social media sites are still struggling to stamp out copies of the gunman's video.

"We're calling on the leaders of tech companies to join with us and help achieve our goal of eliminating violent extremism online at the Christchurch Summit in Paris," Arden said.

The meeting will be held alongside the "Tech for Humanity" meeting of G7 Digital Ministers, and France's separate "Tech for Good" summit also scheduled for May 15.

"We all need to act, and that includes social media providers taking more responsibility for the content that is on their platforms, and taking action so that violent extremist content cannot be published and shared," Ardern said.

"It's critical that technology platforms like Facebook are not perverted as a tool for terrorism, and instead become part of a global solution to countering extremism."

New Zealand has banned both the livestreamed footage of the attack and the manifesto written and released by Brenton Tarrant, who faces 50 murder charges and 39 of attempted murder following the mosque attacks.

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