Facebook Inc. will begin fact-checking photographs and videos posted on the social media platform, seeking to close a gap that allowed Russian propagandists to promote false news during the last U.S. presidential election.

The company said Thursday it will use technology and human reviewers to try to staunch what it called in a statement “misinformation in these new visual formats.” Previously, the company’s efforts had been focused on rooting out false articles and links.

“The...