Facebook, Twitter, and Alphabet collectively removed hundreds of accounts tied to an alleged Iranian propaganda operation on Tuesday, while Facebook took down a second campaign it said was linked to Russia.

Facebook CEO Mark Zuckerberg said the accounts identified on his company's platform were part of two separate campaigns, the first from Iran with some ties to state-owned media, the second linked to sources which Washington has previously named as Russian military intelligence services.

Officials in Iran, where it is a holiday to mark the Muslim Eid al-Adha festival, were not immediately available to comment. Moscow has repeatedly denied using hacking or fake social media accounts to influence foreign elections. The Russian embassy in Washington did not immediately respond to a request for comment.

The move by Facebook and others is the latest attempt by global social media giants to guard against political interference on their platforms. It comes as concerns are rising about foreign attempts to disrupt the U.S. midterm elections in November.

The United States earlier this year indicted 13 Russians for alleged attempts to meddle in U.S. politics, but the latest alleged Iranian activity, exposed by cybersecurity firm FireEye, suggests the problem may be more widespread.

"It really shows it's not just Russia that engages in this type of activity," Lee Foster, an information operations analyst with FireEye, told Reuters.

FireEye said the Iranian campaign used a network of fake news websites and fraudulent social media personas spread across Facebook, Instagram, Twitter, Google Plus, and YouTube, to push narratives in line with Tehran's interests.

The Iranian mission to the United Nations did not respond to a request for comment.

The activity was aimed at users in the United States, Britain, Latin America and Middle East up through this month, FireEye said, and included "anti-Saudi, anti-Israeli, and pro-Palestinian themes" as well as advocacy of policies favorable to Iran such as the U.S.-Iran nuclear deal.

FireEye said the Iranian activity did not appear "dedicated" to influencing the upcoming election, though some of the posts aimed at U.S. users did adopt "left-leaning identities" and took stances against President Donald Trump.

That activity "could suggest a more active attempt to influence domestic U.S. political discourse" is forthcoming, Foster said, but "we just haven't seen that yet."