Facebook and Twitter say they have suspended or removed accounts linked to Iran and Russia over "inauthentic" or "manipulating" behaviour.
More than 650 Facebook pages and groups were said to have been identified as "misleading", according to founder and chief executive Mark Zuckerberg.
Meanwhile Twitter said it suspended 284 accounts with apparent links to Iran.
It comes a day after Microsoft said it had thwarted Russian cyber-attacks against US conservative groups.
On Tuesday, Facebook said it had discovered multiple accounts that displayed "inauthentic behaviour" linked to campaigns that originated in Iran and Russia following investigations that spanned "many months".
"We ban this kind of behaviour because we want people to be able to trust the connections they make," the company said in a statement.
Although the investigation was still in progress, the social media network added, the campaign appeared to be targeting people across multiple internet services in the Middle East, Latin America, the UK and the US.