Facebook removed 1.5 million videos of the New Zealand shooting in the first 24 hours after the mosque attack, the company said late on Saturday.

The suspect appeared to film the shooting on a head-mounted camera which was live-streamed on the social network, renewing scrutiny over tech companies' role in society.

"In the first 24 hours we removed 1.5 million videos of the attack globally, of which over 1.2 million were blocked at upload," Facebook said in a tweet.

The company said it is also removing all edited versions of the video that do not show graphic content out of respect for the people affected by the mosque shooting and the concerns of local authorities.

"We continue to work around the clock to remove violating content using a combination of technology and people," said Mia Garlick of Facebook New Zealand.

New Zealand's Prime Minister Jacinda Ardern on Sunday addressed concerns that social media platforms were exploited by the shooter as video of the attack spread online.

Ardern said she would address the matter and noted that Facebook chief operating officer Sheryl Sandberg had reached out to her.

"Obviously these social media platforms have wide reach," she said. "This is an issue that goes well beyond New Zealand."