Some 82 pages, groups and accounts originating in the Islamic Republic were erased after posting about topics like race relations and immigration in a pattern of “coordinated inauthentic behaviour”, the site said.
It comes after the social network removed hundreds of pages, groups and profiles linked to Iran which posed as news organisations or activists in the English-speaking world back in August.
The network, which has more than two billion users, said some posts targeted Prime Minister Theresa May and Labour leader Jeremy Corbyn while others attacked US President Donald Trump.
The suspicious activity was detected around a week ago, with the US midterm elections coming on November 6.
Around one million accounts followed at least one of the pages, around 25,000 accounts joined at least one of the groups, and one Instagram account had more than 28,000 followers, Facebook’s head of cyber security said.
Writing on the company’s blog, Nathaniel Gleicher said: “Our threat intelligence team first detected this activity one week ago.
“Given the elections, we took action as soon as we’d completed our initial investigation and shared the information with US and UK government officials
“Despite attempts to hide their true identities, a manual review of these accounts linked their activity to Iran.
“We also identified some overlap with the Iranian accounts and pages we removed in August.”
Facebook says it now has more than 20,000 people working on “safety and security” while advances in artificial intelligence mean more fake accounts are being spotted.
“We’re also working more closely with governments, law enforcement, security experts and other companies because no one organisation can do this on their own”, the site said.