As many as 126 million American Facebook users may have seen content uploaded by Russia-based operatives over the past two years, the social networking site said.
According to Facebook, about 80,000 posts were produced before and after the 2016 US presidential election.
Most of the posts focused on divisive social and political messages.
Facebook released the figures ahead of a Senate hearing where it – together with Twitter and Google – will detail Russia’s impact on the social networks.
Russia has repeatedly denied allegations that it attempted to influence the last US presidential election, in which Republican Donald Trump beat Democrat Hillary Clinton.
In a separate major development on October 30, an investigation by independent counsel Robert Mueller into possible collusion between the Trump campaign and Russia produced its first charges against three former aides, and a guilty plea.
Robert Mueller Investigation: Donald Trump’s Campaign Adviser George Papadopoulos Lied About Russia Links
President Donald Trump has dismissed allegations of collusion with Russia, and has repeatedly called on Hillary Clinton to be investigated.
The latest figures released by Facebook have been seen by Reuters and the Washington Post.
The 80,000 posts were published between June 2015 and August 2017.
According to Facebook, they were posted by a Russian company linked to the Kremlin.
Reuters reports that Facebook’s general counsel Colin Stretch said: “These actions run counter to Facebook’s mission of building community and everything we stand for.
“And we are determined to do everything we can to address this new threat.”
The Washington Post reported on October 30 that Google revealed that Russian trolls uploaded more than 1,000 videos on YouTube on 18 different channels.
Meanwhile, Twitter found and suspended all 2,752 accounts that it had tracked to Russia-based Internet Research Agency, a source familiar with the company’s written testimony was quoted as saying by Reuters.