Australia's major telecommunications companies have banned the website Brenton Tarrant used to promote his massacre in Christchurch.
The push came as Prime Minister Scott Morrison wrote to G20 nations asking them to consider practical ways to force companies like Facebook and Google to stop broadcasting atrocities and violent crimes.
Telstra on Tuesday blocked access to 4chan, 8chan and Voat, the blog Zerohedge and video hosting platform Liveleak, because they still hosted footage of the attack.
"We understand this may inconvenience some legitimate users of these sites, but these are extreme circumstances and we feel this is the right thing to do," Telstra networks and IT executive Nikos Katinakis said in a statement.
Optus and Vodafone declined to name which domains they blocked but the same platforms also failed to load on their networks on Tuesday afternoon.
Tarrant, 28, linked to his livestream on 8chan before the attack started.
Vodafone said while blocking requests normally came from the courts or law enforcement agencies "this was an extreme case which we think requires an extraordinary response".
"While there were discussions at an industry level about this issue, this is a decision Vodafone Australia came to independently," a spokeswoman said in a statement.
The attack was live-streamed on Facebook, but none of the 200 people who watched it live reported it using the company's content reporting tools.
"If you can write an algorithm to make sure that the ads they want you to see can appear on your mobile phone, then I'm quite confident they can write an algorithm to screen out hate content on these social media platforms," Mr Morrison told reporters in Adelaide on Tuesday.
Facebook vice president Chris Sonderby confirmed the company has to wait for users to report horrific content, but once it has been reported the company can automatically block people from uploading it again.
New Zealand Prime Minister Jacinda Ardern said social media companies must take responsibility for what they publish.
"They are the publisher. Not just the postman. There cannot be a case of all profit no responsibility," she told parliament.
NSW man Brenton Tarrant has been charged with murder following the shootings at two mosques in Christchurch that killed 50 people and left another 50 injured.
Australian Associated Press