Erling Braut Haaland is in such high demand that even referees are asking for his autograph.

After Borussia Dortmund's 2-1 defeat to Manchester City in the first leg of its Champions League quarterfinal tie on Tuesday, Haaland was hunted down by an assistant referee who was desperate for his autograph.

Romanian linesman Octavian Sovre approached the Dortmund superstar in the tunnel following the match, asking for his signature as other players walked on by.

Haaland duly obliged, signing the assistant referee's yellow card. The incident was caught on camera by BT Sport.