Facebook says it removed more than 100 accounts this week from the main service as well as its subsidiary Instagram over concerns they may be connected to the Russia-based Internet Research Agency (IRA) -- the same troll operation targeted by special counsel Robert Mueller in his sprawling Russia investigation.
The social media giant acknowledged Tuesday that it removed the pages following a tip from the FBI.
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"We blocked over 100 Facebook and Instagram accounts due to concerns that they were linked to the Russia-based Internet Research Agency (IRA) and engaged in coordinated inauthentic behavior, which is banned from our services," says Nathaniel Gleicher, Facebook's head of cyber security policy, on Tuesday.
The company did not disclose details of the pages it removed.
Earlier on Tuesday, a website claiming to be run by the IRA took responsibility for a network of fake social media accounts, many targeting American voters -- an operation similar to what the group orchestrated in the run-up to the 2016 presidential elections.
A message on the website read: "Citizens of the United States of America! Your intelligence agencies are powerless. Despite all their efforts, we have thousands of accounts registered on Facebook, Twitter, and Reddit spreading political propaganda."
The claims were published on Tuesday night as votes in the midterm elections were being counted. CNN has not independently confirmed who controls the pages.
If the pages were run by the IRA, it would represent its most brazen effort since the 2016 presidential election, and a thumb in the eye of American authorities that have tried to undo the power of Russian online disinformation since the last major election.
The group is under indictment by Mueller, whose investigation of the 2016 election has touched the Trump campaign as well as Russians.
Gleicher added: "This evening a website claiming to be associated with the IRA published a list of Instagram accounts they claim to have created. We had already blocked most of these accounts yesterday, and have now blocked the rest. This is a timely reminder that these bad actors won't give up — and why it's so important we work with the US government and other technology companies to stay ahead."
The FBI declined comment.
The accounts CNN reviewed were posted by the group included some pages that were designed to look like they were run by Trump supporters, while other pages targeted African Americans.
Senator Mark Warner, the leading Democrat on the Senate Intelligence Committee, was briefed on the accounts by Facebook, according to his spokesperson. Warner said in a statement provided to CNN on Wednesday, "This shows that Russian influence agents will continue to target the American people and our democratic process. It happened in 2016. We've seen activity in 2018, and I'm confident they will not stop as 2020 remains around the corner."
A DHS official Tuesday said there were "no reported cybersecurity events that would affect the ability to cast and count votes."
On Monday, DHS Secretary Kirstjen Nielsen, Attorney General Jeff Sessions, Director of National Intelligence Dan Coats and FBI Director Christopher Wray released a joint statement that while there was no indication that America's voting infrastructure -- voting machines, for example -- had been compromised, foreign operatives were seeking to influence American voters.
"Americans should be aware that foreign actors -- and Russia in particular -- continue to try to influence public sentiment and voter perceptions through actions intended to sow discord," the statement read. "They can do this by spreading false information about political processes and candidates, lying about their own interference activities, disseminating propaganda on social media, and through other tactics."