Brazilian club Gremio will make a formal complaint after its team bus was attacked by fans of Colombian team Junior Barranquilla. No one was injured.
Three windows were smashed following Gremio's 2-1 loss to Junior in the group stage of the Copa Libertadores on Thursday.
Gremio team official Antonio Vicente Martins has told Radio Gaucha the club will complain to CONMEBOL, the governing body of South American football.
Martins told O Globo newspaper that nearly everybody on the bus was sleeping and thought they had been targeted by gunfire when they were attacked.
The two sides are due to meet again in Brazil in early April.