Facebook Inc. FB, +2.12% and Twitter Inc. TWTR, +1.62% have taken down a global network of fake accounts used in a coordinated campaign to push pro-Trump political messages, including some that used artificial intelligence tools to try to mask the behavior, the companies and outside research firms they worked with said.

President Donald Trump at a roundtable discussion with small-business in the Roosevelt Room at the White House early this month. Getty Images

The move targeted a U.S.-based media company that also operates out of Vietnam called the BL, which, Facebook alleges, used computer-generated profile pictures to cover up the orchestrated nature of its activities. Facebook linked the company to the Epoch Media Group, which has had ties to the Falun Gong movement, a spiritual movement based in China which has clashed with the Chinese government and supported President Trump’s reelection.