The leading social network acknowledged this week it had "paused" some elements of its "graph search," a feature introduced in 2013 which has sparked criticism for allowing posts and other content to be unearthed with a simple query.

But graph search turned out to be an important tool for researchers, rights activists and journalists. It has been used to track activity of suspected war criminals and human traffickers and to monitor extremists.

"We paused some aspects of graph search late last week," a Facebook spokesperson said. "We're in conversations with a few researchers to learn more about how they used this tool."

Jennifer Grygiel, a Syracuse University professor who follows social media, said the move is the latest to tighten data access to Facebook since the scandal over Cambridge Analytica, the consultancy which hijacked personal data of tens of millions of Facebook users.

The new curbs make it harder for researchers to find Facebook posts about topics ranging from war crimes to anorexia to the anti-vaccine movement, Grygiel said.

Grygiel said while the move may be seen as promoting privacy, it also limits the ability of researchers to investigate Facebook itself and its efforts to weed out hate speech and extremist content.

"Researchers like myself were using social graph to show how bad Facebook's content moderation was," she told AFP. "This may be a public relations move because Facebook is tired of having everyone understand how bad their privacy is."

After being introduced in 2013, graph search drew immediate fire from privacy activists as a "creepy" tool that could enable stalking or unwanted disclosures.

Facebook has made changes over the years to graph search and offered users privacy settings limiting what information is unearthed. The company did not respond to an AFP query to elaborate on the most recent changes or the reason for the new policy.

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