Pope Francis is to tackle the rise of fake news in a bid to stop trolls and irresponsible media outlets fomenting hate.

"I have chosen this theme for World Communications Day 2018: 'The truth will set you free'. Fake news and journalism for peace," he said on Twitter on Friday.

Francis has repeatedly warned journalists of the weight of their responsibility in a world dominated by social media.

Last year he compared scandal-obsessed media outlets who smear politicians and spread gossip to people sexually excited by excrement -- and described their readers as faeces eaters.

The Vatican said Friday the Argentine pontiff wanted to tackle "an often misleading distortion of facts" and the spread of "baseless information that contributes to generating and nurturing a strong polarisation of opinions".

"In a context in which the key companies of the social web and the world of institutions and politics have started to confront this phenomenon, the Church too wishes to offer a contribution," it said.

The pope himself was the victim of a fake news story in February. A fake front page fashioned in the same style as the Vatican's official newspaper, which was sent to numerous cardinals and bishops, ran a spoof interview with him.

The World Day of Social Communications, established by the Second Vatican Council, will be celebrated on May 13, though the pope's speech will be released in January on the feast day of the patron saint of journalists.