Facebook plans to hire 1,000 more people to review ads and ensure they meet its terms, as an effort to deter Russia and other countries from using the social media network to interfere in others' elections, it said on Monday.

Facebook said last month that it believed people in Russia bought about 3,000 politically divisive ads on its network in the United States in the months before and after the November U.S. presidential election.

Since its disclosure, Facebook has faced questions and calls for increased U.S. regulation from U.S. authorities.

Facebook said it would add more than 1,000 people over the next year and invest more in software to flag and take down ads automatically.

"Reviewing ads means assessing not just the content of an ad, but the context in which it was bought and the intended audience - so we're changing our ads review system to pay more attention to these signals," the company said.

The company said on Monday that it would adjust its policies further "to prevent ads that use even more subtle expressions of violence."

Facebook also said it would begin to require more thorough documentation from people who want to run ads about U.S. federal elections, demanding that they confirm their businesses or organizations.

Potential advertisers will have to confirm the business or organization they represent before they can buy ads.