Facebook on Friday said it had taken down accounts linked to an Iranian effort to influence US and British politics with messages about charged topics such as immigration and race relations.

The social network identified 82 pages, groups and accounts that originated in Iran and violated policy on coordinated "inauthentic" behavior, Facebook head of cybersecurity policy Nathaniel Gleicher said.

Gleicher said there was overlap with accounts taken down earlier this year and linked to Iran state media, but the identity of the culprits had yet to be determined.

"It's often hard to know who is behind this type of activity," Gleicher said in a telephone briefing.

Account owners tried to hide their identities by passing themselves off mostly as US citizens, and in a few cases as British citizens, according to Gleicher.

Posts on the accounts or pages, which included some hosted by Facebook-owned Instagram, focused mostly on "sowing discord" via strongly divisive issues rather than on particular candidates or campaigns.

The campaign involved the purchase of two online ads, costing a total of $100 paid for in US and Canadian currencies, the first of which ran in June of 2016 and the second of which ran at the start of this year.

The purge involved 30 pages, 33 accounts and three groups at Facebook, as well as 16 accounts at Instagram.

Slightly more than a million accounts followed at least one of the pages, with the majority of the engagement taking place over the past year, according to Facebook.