"On Sunday evening, USA law enforcement contacted us about online activity that they recently discovered and which they believe may be linked to foreign entities", the company said in a statement. Today, the social network removed 30 accounts from Facebook and 85 accounts from Instagram. Offering more detail, the company said that groups and accounts posed as USA or United Kingdom citizens, posting content on divisive topics like race relations and immigration.
The Instagram accounts were mostly in English, with some "focused on celebrities, others political debate".
Facebook said it would provide further information on whether the accounts are linked to the Internet Research Agency, a group linked to Russian propaganda efforts.
The company said it was collaborating with law enforcement agencies, external experts and firms to prevent interference on its platform before and during the elections.
Facebook took down 30 accounts as well as 85 accounts on Instagram, which is also owns after warnings of sustained efforts to affect the result of the USA midterms, which take place today.
She said Russian "trolls", or provocateurs, were likely stoking sentiments on both ends of the USA political spectrum "but that the network we now have identified is targeting the far right of American political discourse".
The company has taken steps to curtail manipulation of its platforms after being widely criticized for allowing Russian trolls spread misinformation during the 2016 election.
The company announced its actions earlier in its investigation than typical "given that we are only one day away from important elections in the USA", he added.
Twitter said Saturday it deleted a "series of accounts" that attempted to share disinformation.
He also pledged to keep the public updated, suggesting Facebook may move to block more suspicious accounts.
The war room is part of stepped up security announced by Facebook, which will be adding some 20,000 employees.