Facebook has said as many as 126 million American users may have seen content uploaded by Russia-based operatives over the past two years.
The social networking site said about 80,000 posts were produced before and after the 2016 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 popular sites.
Russia has repeatedly denied allegations that it attempted to influence the last US presidential election, in which Donald Trump beat Hillary Clinton.
In a separate major development on Monday, an investigation by independent counsel Robert Mueller into possible collusion between the Trump campaign and Russia produced its first charges against two former aides. It also emerged that a third former aide had pleaded guilty in early October to lying to the FBI.
President Trump has dismissed allegations of collusion with Moscow, and has repeatedly called on Mrs Clinton to be investigated.
The latest figures released by Facebook have been seen by Reuters news agency and the Washington Post newspaper.
The 80,000 posts were published between June 2015 and August 2017.
Facebook said they were posted by a Russian company linked to the Kremlin.
"These actions run counter to Facebook's mission of building community and everything we stand for," wrote Facebook's general counsel Colin Stretch, Reuters reports.
"And we are determined to do everything we can to address this new threat."