The European Commission has told firms like Google and Facebook to remove "terrorist content" an hour after it is first notified, or face legislation forcing them to do so.

The European Union has given the world's biggest internet companies an ultimatum: Remove extremist content like this within an hour of first being notified of its existence, or else.

It's part of new guidelines that are the EU's strongest warning yet to the likes of Google, YouTube, and Facebook.

The threat is technically non-binding. But, its authors say they'll bring legislation to force compliance if the tech giants can't demonstrate progress within three months.

And, the guidelines still hold weight in European courts.

European governments have been pressuring internet companies to do more to stop the spread of videos and other media that they say inspires lone wolf militant attacks.