New Zealand Prime Minister Jacinda Ardern has revealed she inadvertently saw social media footage of the Christchurch terror attack, in which 51 people were killed.

Key points: In a New York Times op-ed, Ms Ardern reveals she too had seen the confronting content on social media

In a New York Times op-ed, Ms Ardern reveals she too had seen the confronting content on social media The NZ Prime Minister is preparing to meet with world leaders and seek commitments about preventing the posting of terrorist material online

The NZ Prime Minister is preparing to meet with world leaders and seek commitments about preventing the posting of terrorist material online About 1.5 million copies of the video were shared, despite continuing efforts to remove it

In an opinion piece written for the New York Times, Ms Ardern discussed the details of the attack and its live streaming, saying it was part of a "horrifying new trend that seems to be spreading around the world".

"It was designed to be broadcast on the internet," she wrote in the op-ed, which was published on Saturday.

The reach and speed of the distribution of the almost 17-minute live stream was described by Ms Ardern as "staggering".

She said the original footage was seen about 4,000 times before it was taken down from Facebook, but by the next day 1.5 million copies had been circulated.

"There was one upload per second to YouTube in the first 24 hours," she said.

And due to autoplay features in social media feeds, a large amount of people were exposed to the harrowing vision, unaware, she said.

"I use and manage my social media just like anyone else," she said.

"I know the reach of this video was vast, because I too inadvertently saw it."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 19 seconds 1 m 19 s Jacinda Ardern pays her respects to the Christchurch community.

The piece, headlined "How to stop the next Christchurch massacre", came as Ms Ardern prepared for a meeting with French President Emmanuel Macron and other world leaders, where they hope to develop ways to stop extremist content being shared online.

Following a spate of killings in France in 2016, French mainstream media proprietors decided to adopt a policy of not recycling pictures of atrocities.

"New Zealand will present a call to action in the name of Christchurch, asking both nations and private corporations to make changes to prevent the posting of terrorist content online, to ensure its efficient and fast removal and to prevent the use of livestreaming as a tool for broadcasting terrorist attacks," Ms Ardern said.

"We also hope to see more investment in research into technology that can help address these issues."

Gun laws in New Zealand have already been tightened, with only one politician voting against the measure.

Brenton Tarrant, the Australian man charged with murder and remanded in custody over the terrorist act, had allegedly used five firearms including two semi-automatic weapons, two shotguns and a lever-action firearm in the attack, in the alleged March attack.

The ABC has decided not to broadcast any of the video footage, nor take any quotes from alleged manifesto that has also been shared online.