Russia’s state media censor on Friday summoned representatives of the U.S.-based CNN International cable news television channel over supposed media law violations.

Roskomnadzor spokesman Vadim Ampelonsky told the state-run news agency TASS that CNN had provided an outdated dateline. Documents submitted by CNN to prove they had fixed the problem were “being analyzed,” he said, but the station would remain under observation.

Russia’s Foreign Ministry warned on Thursday that it could retaliate against a U.S. demand for Kremlin-backed news channels RT and Sputnik International to register as foreign agents.

President Vladimir Putin also addressed the “continuing pressure on Russian media in several foreign countries” during a meeting with his national security council, the Kremlin said Friday.

CNN ran several stories this week on Facebook and Twitter ads purchased by Russia’s Internet Research Agency during the 2016 U.S. presidential campaign described as sowing public discord.

Roskomnadzor issued a universal 10-year broadcasting license to CNN in 2015, allowing the channel to sign broadcasting deals with Russian cable and satellite providers.