San Francisco: Facebook Inc said on Tuesday it was tightening rules around its livestreaming feature ahead of a meeting of world leaders aimed at curbing online violence in the aftermath of the Christchurch massacre.

A lone gunman killed 51 people at two mosques in Christchurch on March 15 while livestreaming the attacks on Facebook. It was New Zealand’s worst peacetime shooting and spurred calls for tech companies to do more to combat extremism on their services.

Facebook said in a statement it was introducing a ‘one-strike’ policy for use of Facebook Live, temporarily restricting access for people who have faced disciplinary action for breaking the company’s most serious rules anywhere on its site.

First-time offenders will be suspended from using Live for set periods of time, the company said. It is also broadening the range of offences that will qualify for one-strike suspensions.

Facebook did not specify which offences were eligible for the one-strike policy or how long suspensions would last, but a spokeswoman said it would not have been possible for the shooter to use Live on his account under the new rules.

The company said it plans to extend the new restrictions to other areas over the coming weeks, beginning with preventing the same people from creating ads on Facebook.

It also said it would fund research at three universities on techniques to detect manipulated media, which Facebook’s systems struggled to spot in the aftermath of the attack.

Facebook has said it removed 1.5 million videos globally that contained footage of the attack in the first 24 hours after it occurred. It said in a blog post in late March that it had identified more than 900 different versions of the video.

The announcement comes as New Zealand Prime Minister Jacinda Ardern co-chairs a meeting with French President Emmanuel Macron in Paris on Wednesday that seeks to have world leaders and chiefs of tech companies sign the ‘Christchurch Call,’ a pledge to eliminate violent extremist content online.

In an opinion piece in The New York Times on Saturday, Ardern said the ‘Christchurch Call’ will be a voluntary framework that commits signatories to put in place specific measures to prevent the uploading of terrorist content.

Ardern has not made specific demands of social media companies in connection with the pledge, but has called for them ‘to prevent the use of livestreaming as a tool for broadcasting terrorist attacks.’

Representatives from Facebook, Alphabet Inc’s Google, Twitter Inc and other tech companies are expected to be part of the meeting, although Facebook Chief Executive Mark Zuckerberg will not be in attendance.