The network of pages and accounts that Facebook began to take down on the eve of the midterms over possible connections to a Russian government-linked troll group was followed by more than 600,000 users in the United States, the company said Tuesday.
As in previous efforts run by the Internet Research Agency (IRA), the Russian troll group that has been indicted by Special Counsel Robert Mueller, the pages targeted people across the political spectrum on Facebook as well as on Instagram, which the social media giant owns.
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Some of the Instagram accounts that were part of the network also portrayed themselves as fan accounts for celebrities like Nicki Minaj, Kid Rock and Kendrick Lamar.
Some of the pages posted in French and had very few American followers, the company said.
Facebook said about $4,500 worth of ads were run from the pages but that none of the ads ran in the US. The company did not say where the ads had been purchased from or what currency had been used to buy them.
Facebook, which was criticized for its inaction on tackling Russian disinformation efforts in 2016, said it had taken extensive steps to combat the problem ahead of the midterms -- including setting up an election "war room" at its California headquarters.
But it appears the group behind these pages, some of which had been running for more than a year, managed to avoid detection by the company.
"What's clear is that as we improve our opponents will change their tactics and improve, too. They are smart, well-funded and have every incentive to continue their efforts, even if some of their actions have very little impact," Nathaniel Gleicher, Facebook's head of cybersecurity policy said in a blog post Tuesday.
Last Monday, just hours before Election Day, Facebook said it had removed a network of pages. The company said it was acting on a tip from law enforcement, adding that authorities believed the pages "may be linked to foreign entities."
The following night, a website claiming to represent the IRA took responsibility for operating the pages. Facebook confirmed that the foreign entity *there were concerns about* the network's potential ties to was the IRA.
In Tuesday's blog post, Gleicher wrote, "Ultimately, this effort may have been connected to the IRA, but we aren't best placed to say definitively whether that is the case. As multiple independent experts have pointed out, trolls have an incentive to claim that their activities are more widespread and influential than may be the case. That appears to be true here as well."
Facebook said that combined the pages had about 1.25 million followers, 600,000 of whom were in the US.
A Facebook spokesperson told CNN last week that it had shared details of its findings with other technology companies.
A spokesperson for Twitter said the company had nothing to share. A spokesperson for Google had no immediate comment.