Facebook said on Tuesday it shut down hundreds of pages and accounts operated by Iran- and Russia-backed accounts that concealed their true identities and roped in hundreds of thousands of unwitting users over a seven-year period. Within an hour of Facebook’s announcement, Twitter said it had suspended similar accounts on its platform.

Facebook said four separate and ongoing investigations had so far resulted in the take-down of 652 pages, groups, and accounts, some of which had been identified as early as last August. Twitter announced it had suspended 284 accounts–many of which also originated in Iran–for engaging in “coordinated manipulation.”

Samples from a campaign that Facebook removed including 74 pages, 70 accounts, and three groups on Facebook, as well as 76 accounts on Instagram.

Twitter said it had worked “with our industry peers” to identify the accounts, and reiterated promises to engage “with other companies and relevant law enforcement entities.”

The Iranian efforts may be the first publicly documented instance of an Iran-based influence campaign conducted through U.S. social media. That’s according to security firm FireEye, which tipped Facebook off to the Iranian operation and released its own report. Thus far, Facebook and other social media platforms have largely identified information operations conducted by Russia.

The majority of Facebook’s removals were pages, groups, and numerous Facebook and Instagram accounts connected to pages traced to operators located in Iran. In a blog post Tuesday, Facebook said it saw “coordinated inauthentic behavior that originated…