Facebook’s disclosure in written congressional testimony seen by media on October 30 came as Twitter reported in testimony that it also had found far more accounts linked to the same Russian operatives, the Internet Research Agency, known for promoting pro-Moscow messages.
Both companies are due to testify before the Senate Judiciary Committee about their findings on October 31.
Facebook’s latest disclosure shows that Russian efforts to influence political opinion in the US far exceeded the company’s previous estimate.
In its written testimony, Facebook said the 80,000 posts it found that were published between June 2015 and August 2017 may have reached half of the US population of voting age.
Facebook said most of the posts, which could have been viewed by voters over Facebook’s news feeds or through endorsements and "likes" by other Facebook users, focused on divisive social and political messages such as race relations.
The leading social network said that such "organic" posts that appear in users’ news feeds are distinct from more than 3,000 advertisements linked to the Russian agency that Facebook previously disclosed and turned over to congressional committees.
The ads — many of which also focused on divisive social issues such as race and immigration — directed people to click the advertiser’s pages, where they could then like or share its material.
"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," Facebook General Counsel Colin Stretch said in his written testimony, according to media reports.