Trying to post a black square on Instagram using #BlackLivesMatter? It might be blocked. - USA TODAY

An anti-spam system on Instagram has been "incorrectly" displaying an “action blocked” message to some users, preventing them from posting images using the hashtag #BlackLivesMatter.

"We're aware that some people are incorrectly running into 'action blocked' messages when using the hashtag #blacklivesmatter, or resharing related posts.

Additionally, the trend #BlackoutTuesday, started by music executives Jamila Thomas and Brianna Agyemang, has increased the number of posts on Tuesday using the intended hashtag paired with #BlackLivesMatter.

Instagram acknowledged this issue on Tuesday and exhorted users to "use the hashtag #blackouttuesday, and not #blacklivesmatter" as "the #blacklivesmatter hashtag aggregates important information and resources for the community."

"We want to be clear that using #blacklivesmatter is supported and celebrated on Instagram, and we are moving quickly to ensure voices using this hashtag are heard," Instagram said on Monday