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 offenses that will qualify for one-strike suspensions.

Facebook did not specify which offenses 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. — Reuters