The second leg of the Copa Libertadores final between Buenos Aires rivals River Plate and Boca Juniors has been delayed after River fans attacked the Boca bus as it arrived at the stadium.
Television footage showed River supporters hurling objects at the bus as it made its way to the El Monumental stadium ahead of Saturday night's second leg.
According to reports in Argentina, Boca players suffered cuts from the glass from broken windows and were also taken ill due to the effects of tear gas used by the police to disperse the crowds.
A number of players, including Boca's former Manchester City striker Carlos Tevez, were reportedly suffering from dizziness and vomiting and being treated by club doctors. Footage apparently from inside the Boca dressing room showed the players groggy and disorientated.
CONMEBOL, the South American Football Confederation, announced in a tweet that the final would be postponed by an hour to 1800 local time (2100GMT) as a result of the violence.
The final is finely poised at 2-2 after the first leg two weeks ago.