Telegram, a Dubai-based chat app that has attracted a surge of new users, including some far-right Trump supporters fleeing purges at other sites, has begun a rare purge of American extremist content.

At least 15 extremist Telegram channels — akin to chatrooms where the founders have moderating power — have recently been banned, according to a tally by NBC News. Content has been censored on several others.

Some pro-Trump zealots have moved to Telegram in recent days to plan violence on Jan. 20, the day Joe Biden is scheduled to be inaugurated.

Read more: NBC News