Riot police moved in to restore order after a few punches were thrown and several players were pushed following Brazilian side Internacional's 5-3 aggregate win over Mexico's Guadalajara.
Within seconds of Inter's win, dozens of people ran on to the Beira-Rio pitch in Porto Alegre to celebrate with the players, reserves, members of their families and officials.
"They did not respect the anthem from the start and if they show no respect how can they expect us to respect them?" Mexico midfielder Adolfo Bautista told reporters.
Bautista, who annoyed the Inter fans by warming up during the Brazilian anthem, was quoted in Mexican media as saying a Brazilian team assistant had spat at Marco Fabian de la Mora, who scored Guadalajara's opening goal.
Guadalajara lost the first leg 2-1 at home but raised their hopes of an upset by taking the lead in Wednesday's second leg before going down 3-2.
"We've got to get more used to this type of situation so we don't get distracted," Real told reporters. "But that's not a pretext (for the defeat). Inter are great champions."
