Romania vs Kosovo: Why was it interrupted?

A player clashed with someone who displayed the slogan "Kosovo is Serbia" in the stands. According to the online inquiry of Wuhan Radio and Television, in the 224 European Cup qualifiers, the match was interrupted in the 18th minute because some spectators shouted "Serbia, Serbia", and a player clashed with someone who displayed the slogan "Kosovo is Serbia" in the stands, and the referee sent the player back to the dressing room. Resume the game after a 5-minute break.