A report which appeared in Reuters on Saturday has revealed that Facebook and YouTube are among a group of popular web sites that have begun automatically removing extremist content from their sites

The technology uses unique hashes, or digital fingerprints, to remove Islamic State videos and other similar materials.

The technology can be used to prevent reposts of content already deemed unacceptable but not identify new extremist content.

This is a step towards eradicating violent propaganda from the web in the face of increasingly common terrorist attacks around the world.

In May, Facebook, Twitter, Microsoft and YouTube agreed to a new European Union code of conduct that takes terrorist propaganda posted online.