The efforts include ad purchases on Facebook Inc. FB 0.52% promoting the English-language arms of Chinese state-media outlets, as well as posts there and on Twitter Inc.’s TWTR -0.32% platform that in some cases disparage U.S. efforts to fight the global pandemic, the researchers say.

From mid-February until early March, social-media sites linked to Chinese state media posted more than 3,300 times a day, triple the normal rate, according to Recorded Future, a Somerville, Mass.-based cybersecurity consulting firm. Those outlets were principally active on Facebook and Twitter, the research showed.

The Chinese tweets, researchers say, evoke Russia’s tactics, which involved spreading messages that can incite doubt and stir anger about basic facts and sometimes promote fictitious claims. Russia also leaned heavily on state media to spread its message online.