YouTube, Facebook, Twitter and Microsoft are setting up a joint database to fight terrorist content online, the four US tech giants said in a joint statement.

The companies plan to create a shared industry database of unique digital "fingerprints", known as "hashes," for violent terrorist imagery, terrorist recruitment videos or other type of extremism-related content. The exchange of such data will help to take swifter action against extremist content.

"Our companies will begin sharing hashes of the most extreme and egregious terrorist images and videos we have removed from our services - content most likely to violate all of our respective companies’ content policies," the statement reads.

"Participating companies can add hashes of terrorist images or videos that are identified on one of our platforms to the database. Other participating companies can then use those hashes to identify such content on their services, review against their respective policies and definitions, and remove matching content as appropriate," the statement continues.

Each company will independently determine what image and video hashes should be added to the shared database. Matching content will not be automatically removed.

The statement gives no reasons behind the move, but media reported in February that the US administration requested assistance from the country’s leading technology companies in fighting against content posted by the radical Islamic State group (outlawed in Russia) on social networking websites.

About a year ago the same quartet of companies joined efforts to identify and remove child pornography using a similar technique, developed by the UK’s Internet Watch Foundation.