The second match of the Copa Libertadores final between Argentine powerhouses Boca Juniors and River Plate was postponed indefinitely Sunday after River Plate hooligans attacked a Boca team bus the day before, according to the governing body of South American football.
It is not clear when the game might be rescheduled, but the presidents of the two clubs, who are fierce rivals, will meet in Paraguay Tuesday.
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Boca Juniors captain Pablo Pérez and midfielder Gonzalo Lamardo were treated at a hospital after River Plate fans threw projectiles at their team bus on its way to the River Plate stadium in Buenos Aires, Argentine state TV station Telam reported.
Almost 2,000 police officers were deployed to the stadium area, CNN affiliate TN reported. Twenty-nine River Plate fans were arrested, TN reported.
Alejandro Dominguez, president of the South American confederation known as CONMEBOL, condemned the violence and urged authorities to find those behind the attacks.
"What must have been a sporting event to live, enjoy and share the best of South American football became a shame," he tweeted Saturday night.
"CONMEBOL condemns the violent and criminal acts that put lives at risk, threatened the livelihood of professional athletes, affected millions of good fans and embarrassed their team, their football, their country and their continent."
No visiting fans allowed
Hours before the attack, hundreds of Boca's blue-and-yellow-clad fans surrounded the hotel where their team was staying, the players shared on social media. Saturday's match was open only to supporters of the home team, River Plate, due to the rising tensions.
When the team was on its way to River's Estadio Monumental, Boca players encountered a moving mass of white and red near the stadium and some River Plate fans began throwing projectiles and stones at their bus, shattering the vehicle's windows, Telam reported.
The tear gas police used to disperse the crowds made its way inside the bus and affected some players.
By the time they made it inside the stadium, players Carlos Tevez, Cristian Espinoza and Mauro Zárate had difficulty breathing and coach Guillermo Barros Shelotto was coughing, Telam reported.
The Super Clasico's final leg was initially delayed at least three times Saturday as tens of thousands of fans waited inside and outside the stadium as players also voiced their concerns.
"They are forcing us to play the match in these conditions," Tevez, Boca's captain, told reporters during the delay. "The truth is that we have three colleagues who are not physically OK."
The two teams agreed to play Sunday evening -- Boca fans were angry that club president Daniel Angelici had signed the agreement -- but CONMEBOL later announced the game was canceled indefinitely.
The G20 leaders summit is set to begin in Buenos Aires on Friday, requiring a heavy Argentine security presence.
The match will decide the club champion for South America (top Mexican teams also were invited). The two teams drew 2-2 in the first match of the final series.
Boca Juniors has won the competition six times, most recently in 2007. River Plate won the title in 1986, 1996 and 2015. The two sides are competing for the title for the first time in the tournament's nearly 60-year history.
History of crowd trouble
Boca and River are the biggest clubs in Argentina and have a long and distinguished rivalry.
Since the first official match in 1913 -- which River won 2-1 -- the two clubs have gone on to become the dominant forces in Argentina. Diego Maradona played for Boca in the early 1980s before signing for Spanish club Barcelona.
What started out as a small, local rivalry in the working class La Boca neighborhood of Buenos Aires gradually grew to be the biggest in the country, with River gaining a reputation as the club for the rich and Boca as the working man's team.
And that rivalry has often been accompanied by trouble between fans off the pitch.
In 2015, Boca was booted out of the Copa Libertadores after its fans pepper-sprayed players from River during the round of 16.
The incident happened at Boca's Bombonera stadium as players emerged for the second half of a finely balanced two-legged match. The score was tied at 0-0 on the night with River leading 1-0 from the first leg at its crosstown Monumental Stadium a week earlier.
The match was abandoned shortly afterward, and four River players were taken to a hospital for treatment.
Two years earlier, another fixture at La Bombonera was halted for 15 minutes after riot police were brought in to deal with fighting in the stands.
Since 2013, there have been no away fans allowed in stadiums across Argentina after a Lanus fan was shot and killed by a policemen before a match at Estudiantes.
Copa Libertadores, South America's most prestigious club competition, has also had safety issues in the past. In 2013, a Bolivian fan was killed by a flare fired by supporters of Brazilian club Corinthians.