The European Union is set to impose one-hour deadlines on Facebook, Twitter, YouTube and other internet companies to identify and delete online terrorist propaganda and extremist violence or face fines.
The Financial Times has learned that the EU is drafting legislation to force these companies to delete material when law enforcement flags it as terrorist-related.
The companies will have three months to show that they are removing extremist content more rapidly or face legislation forcing them to do so.
Social media companies have come under increasing pressure from various governments and the EU to do more to combat extremism and remove content such as hate speech and Islamic State propaganda.
The European Commission said last week that internet firms should be ready to remove extremist content within an hour of being notified and recommended measures they should take to stop its proliferation.
The European Union is no longer convinced that self-policing is enough to purge online extremist content.
Julian King, the European commissioner for security, argued that a law was necessary as officials had "not seen enough progress" through the existing approach. Europeans "cannot afford to relax or become complacent" in dealing with extremism, he said.
A senior EU official told the FT that new legislation would "likely" mandate removing content within an hour of receiving notice, turning the existing voluntary guidelines into an absolute requirement.
The EU is poised to publish the draft legislation in September. The European Parliament and individual member nations would still have to wait for the finished proposal and vote on it before it could take effect, so it may be months later before there's any definitive action.
The Guardian reports that the EU has urged the predominantly US-dominated technology sector to adopt a more proactive approach, with automated systems to detect and remove illegal content, something Facebook and Google have been pushing as the most effective way of dealing with the issue.
However, the European Digital Rights group described the Commission's approach as putting internet giants in charge of censoring Europe, saying that only legislation would ensure democratic scrutiny and judicial review.
New legislation would not be a major issue for big tech that can recruit more content moderators, but it could be for smaller sites. The UK government recently unveiled its own AI-powered system for tackling extremist propaganda online, which could be offered to smaller companies.