San Francisco (AFP) - Facebook said Thursday it would launch fact-checking of photos and videos as it expands the effort to curb misinformation to more countries.

The huge social network, which has been a frequent target for failing to stop the spread of false news, said it will use machine learning and other technical tools for its effort to clamp down on manipulated images and videos.

"One challenge in fighting misinformation is that it manifests itself differently across content types and countries," said a blog post from Facebook product manager Tessa Lyons.

"To address this, we expanded our test to fact-check photos and videos to four countries. This includes those that are manipulated (e.g. a video that is edited to show something that did not really happen) or taken out of context (e.g. a photo from a previous tragedy associated with a different, present day conflict)."

After being blamed for allowing misinformation and manipulation during the 2016 US election, Facebook has stepped up efforts to clamp down on fake accounts and the spread of hoaxes, rumors and other false information.

Lyons said Facebook's fact-checking efforts is now in place in 14 countries, with more to be added this year, using independent partners to verify information.

"These certified, independent fact-checkers rate the accuracy of stories on Facebook, helping us reduce the distribution of stories rated as false by an average of 80 percent," she said.

She added that Facebook was working to identify "repeat offenders" as part of the fact-check effort.

"Historically, we have used ratings from fact-checkers to identify pages and domains that repeatedly share false news," she said.

"We then take action by reducing their distribution and removing their ability to monetize. To help curb foreign interference in public discourse, we are beginning to use machine learning to help identify and demote foreign pages that are likely to spread financially motivated hoaxes to people in other countries."

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