Twitter announced last week that it was introducing new online tools to tackle “behaviors that distort and detract from the public conversation.” The social media company faced criticism after thousands of Russian-linked accounts were found to have disseminated propaganda that attempted to stoke racial and political tensions during the 2016 U.S. presidential election campaign.

Bulgarian users of Twitter have reportedly been subject to widespread bans for writing tweets in Cyrillic after the social network introduced measures against Russian bots.

Since the announcement, a number of users in the Bulgarian Twitter community had their accounts suspended and tweets muted, the Verge tech news website reported Tuesday.

“The most likely explanation is that Twitter has ramped up its algorithms for weeding out Russian bots and trolls, and since Russians use Cyrillic, the very use of the alphabet is being treated as a red flag,” the outlet wrote.

Twitter said it will “take any needed steps to resolve” the issue while continuing efforts to “combat malicious networks of spam and automation.”

According to testimony to a U.S. Senate panel on Russian meddling last fall, Twitter said it considers “whether the user frequently Tweets in Russian” or “the user’s display name contains Cyrillic characters” in determining if the account is Russian-linked.