"We're still in the very early stages of our investigation and don't have all the facts -- including who may be behind this," Facebook said in a series of blog posts.

"But we are sharing what we know today given the connection between these bad actors and protests that are planned in Washington next week."

The company said it removed 32 accounts from Facebook and Instagram because they were involved in "coordinated" political behavior and appeared to be fake.

Facebook stopped short of saying the effort was aimed at influencing the U.S. midterm elections in November, although the timing of the suspicious activity would be consistent with such an attempt.

According to a Facebook official, the company held briefings in the House and Senate this week. The official declined to be named because the briefings were private. Facebook disclosed its findings after The New York Times reported on them earlier Tuesday.

The company said it doesn't know who is behind the efforts, but said there may be connections to Russia. Facebook said it has found some connections between the accounts it removed and the accounts connected to Russia's Internet Research Agency that it removed before and after the 2016 U.S. presidential elections.

The earliest page was created in March 2017. Facebook says more than 290,000 accounts followed at least one of the fake pages. The most followed Facebook Pages had names such as "Aztlan Warriors," ''Black Elevation," ''Mindful Being," and "Resisters."

Facebook says the pages ran about 150 ads for $11,000 on Facebook and Instagram, paid for in U.S. and Canadian dollars. The first ad was created in April 2017; the last was created in June 2018.

The company added that the perpetrators have been "more careful to cover their tracks" than in 2016, in part because of steps Facebook has taken to prevent abuse over the past year. For example, they used virtual private networks and internet phone services, and paid third parties to run ads on their behalf.

More about: Facebook