Facebook said that an operation spent $100,000 on thousands of US ads promoting divisive social and political messages in a two year period through May.

Facebook, the dominant social media network, said 3,000 ads and 470 “inauthentic” accounts and pages spread polarising views on topics including immigration, race and gay rights.

Another $50,000 was spent on 2,200 “potentially politically related” ads, likely by Russians, Facebook said.

US election law forbids foreign nationals and foreign entities from spending money to expressly advocate the election or defeat of a candidate. Non-US citizens are only allowed to advertise on issues and not endorse a candidate. Adverts which mention a candidate but do not call for the candidate’s election or defeat, fall into what lawyers have called a legal gray area.

Facebook announced the findings in a blog post by its chief security officer, Alex Stamos, and said that it was cooperating with federal inquiries into influence operations during the 2016 US presidential election.

Facebook briefed members of both the Senate and House of Representatives intelligence committees on Wednesday about the suspected Russia advertising, according to a congressional source familiar with the matter. Both committees are conducting probes into alleged Russian interference in the 2016 US election, including potential collusion between the campaign of President Donald Trump and Moscow.

Facebook also gave its findings to Robert Mueller, the special counsel in charge of investigating alleged Russian interference in last year’s presidential election, a source familiar with the matter said. The company produced copies of advertisements as well as data about the buyers, the source said.

Facebook said it found no link between the Russian-purchased advertising and any specific presidential campaign. The ads were mostly national in their focus and did not appear to reflect targeting of political swing-states, the company said.

Even if no laws were violated, Facebook said the 470 accounts and pages associated with the ads ran afoul of the social network’s requirements for authenticity and have since been suspended.

Facebook did not print the names of any of the suspended pages, but some of them included such words as “refugee” and “patriot”.

More than $1 billion was spent on political ads during the 2016 presidential campaign, thousands of times more than the presumed Russian spending identified by Facebook’s security team.

The findings buttress US intelligence agency conclusions that Russia was actively involved in gaming the US election to get President Donald (Prince of Orange) Trump elected.

Until recently, Facebook has insisted it was not being played by the Russians. As recently as June, Facebook told journalists that it had not found any evidence of Russian operatives buying election related ads on its platform.

Representative Adam Schiff, the top Democrat on the House Intelligence Committee, called the Facebook report “deeply disturbing and yet fully consistent with the unclassified assessment of the intelligence community”.

A Facebook employee said Wednesday that there were unspecified connections between the divisive issue ads and a well-known Russian “troll factory” in St. Petersburg that publishes comments on social media as part of President Putin’s propaganda campaigns.