Facebook Inc says it removed a staggering 1.5 million videos showing harrowing viral footage of the Christchurch mosque rampage but criticism of social media giants for failing to block images of the "real-time terror attack" is also spreading fast. As the gunman callously picked off his victims in Christchurchs Al Noor mosque, he livestreamed the gruesome scene on Facebook Live, apparently using a camera mounted on his body, after also tweeting a racist "manifesto." Facebook said it "quickly" removed the video, plus the gunmans account and Instagram, and in the first 24 hours scrubbed 1.5 million videos worldwide "of which 1.2 million were blocked at upload." The death toll in the New Zealand mosque shootings rose to 50 on Sunday. The gunman attacked two mosques during Friday prayers. Spokeswoman Mia Garlick from Facebook New Zealand said the firm was "working around the clock to remove violating content using a combination of technology and people." But despite pleas -- and official orders from authorities -- not to share the content, the footage proliferated widely online and experts said the 17-minute video was easily retrievable several hours after the attack that killed 50 people. According to Facebooks own figures, at least 300,000 videos were not blocked before being uploaded and there is no official data on how many times these were viewed or shared. New Zealand Prime Minister Jacinda Ardern said authorities did whatever they could to purge the web of the images but laid the responsibility at the door of the Silicon Valley giants. "Ultimately it has been up to those platforms to facilitate their removal," she told reporters. "I do think that there are further questions to be answered. Obviously these social media platforms have wide reach. This is a problem that goes well beyond New Zealand." "This is an issue that I will look to be discussing with Facebook," she warned. Facebook has hired about 20,000 moderators but critics say they are not doing enough. David Ibsen, executive director of US-based Counter Extremism Project, charged: "The technology to prevent this from happening is available. Social media firms have made the decision not to invest in adopting it." And world leaders and authorities are beginning to indicate they may try to take matters into their own hands. Australian Prime Minister Scott Morrison acknowledged that while social media companies have indicated willingness to take action, "clearly the capability to deliver on that willingness hasnt been present. That is the problem." "There needs to be the capability to be able to shut this -- these horrific things -- down immediately and if you cant do that, then the responsibility of having those features available is something that really generally needs to be questioned," he added. British Home Secretary Sajid Javid also urged social media giants to do more. "Take some ownership. Enough is enough."