Facebook said Wednesday that phony accounts that appear to have originated in Russia bought $100,000 worth of advertisements during the 2016 U.S. presidential campaign and in the months following the election.

Most of the ads didn’t specifically mention the election or express support for a particular candidate. But they did appear to “focus on amplifying divisive social and political messages across the ideological spectrum touching on topics from LGBT matters to race issues to immigration to gun rights,” said Facebook Chief Security Officer Alex Stamos in a post on the social networking site.

Between June 2015 and May of this year, roughly 3,000 ads connected with 470 “inauthentic accounts” ran on Facebook, according to the company. “Our analysis suggests these accounts and pages were affiliated with one another and likely operated out of Russia,” it said.

A Facebook official confirmed to CBS News that some of the accounts are linked to a troll farm called the Internet Research Agency in St. Petersburg.

Facebook said it shut down the fake accounts that were still active, but did not specify the number.

The Washington Post, which first reported the news, described the ad operation as a “troll farm” and said it sought to target U.S. voters. A small number of the ads mentioned either then-candidate Donald Trump or Hillary Clinton by name.

Facebook has been struggling with the issue of fake accounts, including organizations seeking to promote posts and generate traffic using bots.

Earlier this year, it purged tens of thousands of accounts that had shown up as “likes” and followers on pages belonging to media outlets. It deleted 30,000 accounts in the run-up to the French national election in May, an event that allegedly also ilvolved fake accounts linked to Russia.