Pep Guardiola was sent off at half-time of Manchester City's Champions League quarter-final second leg with Liverpool after confronting the referee on the pitch.
The Manchester City boss ran onto the turf at the Etihad Stadium shortly after Antonio Lahoz brought the first half to an end, having controversially accounted for no time stoppage time.
A number of City players addressed Lahoz before he was faced by a clearly irate Guardiola, whose remonstrations prompted the official to send him to the stands.
City took a 1-0 lead into the break courtesy of Gabriel Jesus' second-minute strike, but the home fans had grown frustrated with certain decisions throughout the half.
Lahoz opted to book Sadio Mane for a careless lunge on Nicolas Otamendi and also showed a yellow card to City goalkeeper Ederson for pushing the Liverpool forward, with five yellow cards shown in total in the first 45 minutes.
Leroy Sane had a goal controversially disallowed towards the end of the half, with the offside flag denying the German despite James Milner having deflected the ball into the City forward's path.
Lahoz's decision not to add on any additional time prompted boos from the crowd and saw City players and coaching staff speak to him before he left the pitch.
The Spaniard was in charge of City's first leg of their last-16 exit to Monaco last season, in which Guardiola was incensed that a penalty was not awarded to Sergio Aguero when the scores were level at 1-1.
