"These were distinct campaigns and we have not identified any link or coordination between them," the Menlo Park, California-based social media giant said in a statement posted online. "However, they used similar tactics by creating networks of accounts to mislead others about who they were and what they were doing."
"We ban this kind of behavior," the statement continued, "because we want people to be able to trust the connections they make on Facebook. And while we're making progress rooting out this abuse, as we've said before, it's an ongoing challenge because the people responsible are determined and well funded."
Facebook's market cap at the close of business on Tuesday was approximately half a trillion dollars.
"There is always a tension between taking down these bad actors quickly and improving our defenses over the long term," Facebook's statement continued. "If we remove them too early, it's harder to understand their playbook and the extent of their network. It also limits our ability to coordinate with law enforcement, who often have investigations of their own."
The statement included comments attributed to Nathaniel Gleicher, head of cybersecurity policy, who said Facebook has removed "652 pages, groups and accounts for coordinated inauthentic behavior that originated in Iran and targeted people across multiple internet services in the Middle East, Latin America, UK and US."
"We're working closely with U.S. law enforcement on this investigation, and we appreciate their help," Gleicher wrote. "These investigations are ongoing -- and given the sensitivity we aren't sharing more information about what we removed."
Sen. Mark Warner, D-Va., vice chair of the Senate Select Committee on Intelligence, said in a statement after Facebook's announcement that "this is further evidence that foreign adversaries are actively using social media to divide Americans and undermine our democratic institutions."
"I've been saying for months," Warner's statement continued, "that there's no way the problem of social media manipulation is limited to a single troll farm in St. Petersburg, and that fact is now beyond a doubt. We also learned today that the Iranians are now following the Kremlin's playbook from 2016. While I'm encouraged to see Facebook taking steps to rid their platforms of these bad actors, there's clearly more work to be done."
Executives from Facebook, Twitter and Google are expected to field more questions from the Senate Intelligence Committee at a hearing on Sept. 5.
Twitter also announced late Tuesday that it had suspended 284 accounts "for engaging in coordinated manipulation."
"Based on our existing analysis," the company said in a Tweet, "it appears many of these accounts originated from Iran."