Russia has complained to both Facebook and Google, claiming adverts they circulated "interfered" with elections in the country.
The adverts were seen on social media and the web while local elections were under way in Russia this weekend.
Facebook said Russia should talk to advertisers, who were responsible for complying with local laws.
Google said it supported "responsible" political advertising that complied with Russian laws.
Russia's communications watchdog Roskomnadzor said Google and Facebook had flouted its demand to ban political advertising while voting was under way across the country.
"Such actions can be seen as interference in Russia's sovereign affairs and hindering the conduct of democratic elections in the Russian Federation," it said in a statement.
Russian laws put strict limits on when political adverts can be run and demands they are not seen while elections are ongoing.
In response, Facebook said it was up to advertisers to make sure their messages were sent out at appropriate times.
In a statement given to Reuters, Google said any adverts had to "comply with local legislative demands including the laws on elections and voting rights and mandatory 'election silence' for any geographical areas where such advertising is oriented".
The Roskomnadzor complaint comes soon after Russia rebuked Google for letting YouTube users share information about protests in the country.
Regulators called on Google to remove the videos or face punishment.