Palmeiras overturned a two-goal deficit to beat Penarol 3-2 but the Copa Libertadores clash was overshadowed by a brawl.
After Willian's second-half brace completed a stunning comeback in Montevideo, tensions boiled over between hosts Penarol and Group 5 leaders Palmeiras, and both sets of fans in the Uruguayan capital.
Former Inter, Galatasaray and Juventus midfielder Felipe Melo - now playing for Palmeiras - could be seen swinging punches before he was chased down the pitch by Penarol players.
One Penarol player picked up a corner flag before police intervened as the violence spilled over into the stands at Estadio Campeon del Siglo.
Prior to the commotion, Penarol looked to be on track for a crucial victory thanks to Mauricio Affonso and Junior Arias.
Affonso opened the scoring with a 13th-minute volley and Arias made it 2-0 when he fired the ball past Fernando Prass 26 minutes later.
However, Willian triggered Palmeiras' comeback after stunningly volleying the ball into the top corner of the net four minutes into the second half.
Yerry Mina equalised just past the hour-mark before Willian completed the fightback with 17 minutes remaining as Palmeiras moved four points clear atop the group.
Atletico PR leapfrogged Brazilian rivals Flamengo at the top of Group 4 after prevailing 2-1.
Robinho was on target as Group 6 leaders Atletico Mineiro beat Libertad 2-0, while Medellin upstaged Melgar 2-1 in Group 3.