A masked fan unplugged a video assistant referee (VAR) monitor during a German second-division match on Sunday as the referee went to the pitchside screen to check a penalty award.

The incident occurred at the end of the first half of Preussen Munster's 2-1 home defeat by Hertha Berlin in Bundesliga 2.

VAR had intervened, and referee Felix Bickel was asked to review the incident on a pitchside monitor, but found the screen blank.

"A masked spectator from the active fan section illegally entered the pitch and unplugged the technical equipment," Preussen Munster said in a statement.

With Bickel unable to make the call, the decision was left to the VAR official, Katrin Rafalski, in Cologne, who ruled it a foul and directed Bickel to award a penalty, which Hertha scored.

"Preussen Munster regrets the incident and will do everything in its power to identify and bring the perpetrator(s) to justice," the club added.

"Furthermore, immediate measures have been taken to prevent similar incidents in the future. Initial findings indicate that this was a planned action - a banner to that effect was displayed in the home section shortly after the technical malfunction."

German media reported that a banner reading "Pull the plug on VAR" was displayed.