Facebook, Twitter, YouTube and Microsoft have agreed to block illegal hate speech from their European services in less than 24 hours.

The new European Union "code of conduct on illegal online hate speech" states that the four internet companies will review reports of hate speech in less than 24 hours and remove the content or disable access if necessary.

This latest move is in response to a surge in antisemitic, anti-immigrant and pro-Islamic State commentary on social media.

While the companies downplayed the significance of the deal, some experts believe the EU agreement is part of a broad trend toward more government restrictions.

"Other countries will look at this and say, 'this looks like a good idea, let's see what leverage I have to get similar agreements,'" said Daphne Keller, a former associate general at Google.

"Anybody with an interest in getting certain types of content removed is going to find this interesting."