SAN FRANCISCO – Facebook has uncovered a covert Iranian disinformation campaign which attempted to sow political discord in the U.S. over such hot-button issues as race, immigration, police brutality and President Trump ahead of the November midterm elections.

The social media giant said Friday it detected the activity coming from dozens of pages, accounts and groups on Facebook and Instagram late last week. Facebook removed 82 Facebook pages, groups and accounts for "coordinated inauthentic behavior" that originated in Iran and targeted people in the U.S. and U.K. over the course of the last year, the company said.

The Facebook announcement, coming two weeks before the midterms, was a bracing reminder of the growing scale and frequency of disinformation operations threatening the United States on social media, some of it tied to foreign governments, even as Facebook adds thousands of new employees and strengthens technology to more quickly root out and take down disinformation campaigns.

The page administrators and account owners typically misrepresented themselves as U.S. citizens, or in a few cases U.K. citizens, to post on politically divisive subjects ripped from the headlines such as the confirmation hearings of Supreme Court Justice Brett Kavanaugh. Last week Twitter disclosed more than 1 million tweets from the same operation.

"We have found no ties at this point to the Iranian government," Nathaniel Gleicher, head of cybersecurity policy, told reporters in a conference call Friday. He could not say for certain who was behind the operation. The investigation is ongoing and Facebook is working with federal law enforcement, he said.

Iran and Russia have denied any involvement in Facebook disinformation campaigns.

In August, Facebook disclosed a propaganda operation that it traced to Iranian state media, the biggest of its kind since Russian operatives spread propaganda to sow political discord during and after the 2016 presidential election. That operation focused on pro-Iranian messaging.

The Atlantic Council’s Digital Forensic Research Lab's Ben Nimmo, who reviewed 10 Facebook pages and 14 Instagram accounts 12 hours before they were taken down, says the Iranians evolved their propaganda tactics, masquerading as left-leaning Americans to amplify divisions over politically charged issues in the U.S. A much smaller portion of the activity was focused on more typical Iran government narratives such as attacks on Saudi Arabia and Israel.

The U.S. midterm elections figured prominently in the posts. Some either directly discussed voting or called on others to vote, The Atlantic Council found.

Some of the Facebook pages had large followings and high numbers of shares. One, called I Need Justice Now (@INeedJusticeNow), had more than 13 million video views. Another, No Racism No War (@nornowar), garnered more than 412,000 likes and nearly half a million followers. And two of the most popular pages were recently created: @VoiceofChangee, with 113,155 followers, and @INeedJusticeNow, with 61,507 followers, were created this year, on February 3 and April 1, Nimmo said.

The tactics – to stir outrage on race and Trump among other divisive subjects using a combination of original content and content taken from legitimate websites - were taken straight from the Russian disinformation playbook, Nimmo said. And they worked: propaganda on Facebook and Instagram and Facebook received large numbers of shares and replies.

"This looks like an Iranian disinformation operation that has learned from the Russian operations," Nimmo said.

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Iran maintained 30 pages, 33 accounts and three groups on Facebook and 16 accounts on Instagram, the company told reporters. Some 1 million Facebook accounts followed at least one of the pages, about 25,000 Facebook accounts joined at least one of the groups and more than 28,000 accounts followed at least one of the Instagram accounts.

Less than $100 was spent on two ads paid for in U.S. and Canadian dollars on ads on Facebook and Instagram. The first ad ran in June 2016 and the second in January 2018.

Facebook says it has not completed its review of the Iran content, but pages associated with it hosted seven events. Gleicher declined to say how many people viewed the posts or signaled they were interested in attending or attended the events.

Unlike the previous activity which tried to direct Facebook users to websites, this part of the campaign focused on social media, Nimmo said.

The foreign policy messages from the Facebook and Instagram accounts were in line with the pro-Iranian government messaging on the Middle East by a previous operation that Facebook tied to Iranian state media, The Atlantic Council said.

In August, Facebook disclosed that people with ties to Iranian state media set up social media accounts with fake names to target liberal groups, such as supporters of Sen. Bernie Sanders, I-Vt., in the USA or Scottish separatists in the U.K.

A USA TODAY review of the social media posts in August showed they then tapped into resentment on topics such as the conflict between Israel and the Palestinians, immigration and Britain's vote to leave the European Union. They also pushed pro-Iranian messages alongside anti-Trump messages or posts backing Jeremy Corbyn, leader of Britain’s opposition Labour Party.

The objective of that campaign: to hijack the political conversation to promote anti-Israeli, anti-Saudi and pro-Palestinian themes and Tehran's interests around the globe, including U.S. policies favorable to Iran such as a nuclear deal, which Trump scrapped in May, that had lifted sanctions, researchers told USA TODAY.These are examples of the Facebook ads: