New York (CNN Business) Reddit has warned users of its forum for President Trump supporters that "systematic harassment" of the alleged potential whistleblower whose complaint kicked off the impeachment inquiry "must stop immediately." The company cited in part its policy prohibiting "inviting vigilantism."

The Reddit forum, known as "The_Donald" subreddit, has previously been embraced by Trump and his inner circle.

In a message to the Trump supporters that run the forum that was posted Tuesday, Reddit staff said, "posts that do nothing more than attempt to focus mob attention on this alleged individual cross a line." The company said it had seen a "dramatic rise" in these types of posts in recent days.

"Please note that our rules about harassment and our prohibitions on inviting vigilantism still apply to any discussions speculating about the whistleblower's identity," they added.

In response, users of the forum have promoted alternative sites to continue communicating in case Reddit shuts The_Donald down.