Twitter is abuzz with what appears to be a post-it-note war between buildings on Canal Street.

Twitter user @kBostley alerted NY1 to the apparent war.

The agency Havas Worldwide, which lists its location at 200 Hudson Street on its Facebook page, posted about the "war" on its Facebook and Twitter pages, and claims the war is between its company and Horizon Media, located across the street.

Users have been posting images of the post-it-note war under the hashtag #canalnotes.