High-tech companies should develop "spell-checkers" to censor Daesh on social media, the head of Google, the world's biggest internet search engine, has said.

Eric Schmidt, Google's executive chairman, said new steps were needed to block the spread of gruesome videos and violent propaganda. Such measures were technically "within reach", The Telegraph reported.

He said the internet's rapid growth had made it "too easy" for people to make contact with others in different parts of the world to spread violent ideas rather than using it to broaden horizons.

"We should build tools to help de-escalate tensions on social media — sort of like spell-checkers, but for hate and harassment," Schmidt wrote.

Schmidt's call came just days after a married couple, Syed Rizwan Farook and Tashfeen Malik, carried out a deadly attack in the California city of San Bernardino, killing 14 people. Malik is said to have posted a pledge of allegiance to Daesh in the moments before the massacre.

Schmidt said it was technologically feasible to stop such virtual recruitment.

He said the internet was "allowing some of our worst traits — in the form of envy, oppression and hate — to come into full view".

"We need strong leaders worldwide who will fight broadly for human progress and tolerance, and focus on bettering everyone’s lives," he added.