SAN FRANCISCO • Facebook will prioritise "trustworthy" news in its feed of social media posts, using member surveys to identify high-quality outlets and fight sensationalism and misinformation, said chief executive officer Mark Zuckerberg.

The company, which has more than two billion monthly users, said its members, not experts or Facebook executives, would determine how news outlets rank in terms of trustworthiness.

It also said that it would put an emphasis on local news sources.

The move is likely to send shockwaves through the media landscape in nearly every country, given the ubiquity of the world's largest social network and how central it has become in some places to the distribution of news.

Mr Zuckerberg said on Friday that he expects recently announced changes to shrink the amount of news on Facebook by 20 per cent, to about 4 per cent of all content from 5 per cent currently.

The chief executive outlined the shake-up in a post on Facebook, saying that starting this week, the News Feed - the company's centrepiece product - would prioritise "high-quality news" over less trusted sources.

"There's too much sensationalism, misinformation and polarisation in the world today," wrote Mr Zuckerberg.

"Social media enables people to spread information faster than ever before, and if we don't specifically tackle these problems, then we end up amplifying them."

The quality of news on Facebook has been called into question after alleged Russian operatives, for-profit spammers and others spread false reports on the social media platform, including during the 2016 United States presidential election campaign.

The change will affect not only links posted by news outlets, but also news stories that individuals share, Facebook said.

REUTERS