The final of the Copa Libertadores, the equivalent of Europe's Champions League, is finely poised at 2-2 following the first leg at Boca's Bombonera stadium two weeks ago.
There were desperate attempts to stage the game on its scheduled day, first with an hour's delay, at 6pm local time, and then at 7.15, 7.30 and 7.45, before the abandonment was finally announced to deafening whistles from the 70,000 inside the ground at around 7.20.
The attack shattered several of the bus windows and Boca players were cut by broken glass and also suffered from smoke inhalation due to tear gas. Fans of River Plate were seen attacking the bus of Boca as it neared the Estadio Monumental, and it turns out players of Boca were hurt as a result.
"They were throwing pepper gas, stones, everything", the Clarin website quoted Juan Carlos Crespi, a member of the Boca delegation, as saying.
There were unconfirmed reports of six Boca players vomiting due to pepper spray inhalation - with claims it was River fans, not the police, who used the gas.
Just minutes before the delayed kick-off, the teams had still not warmed up on the field. "They're forcing us to play the game".
A riot policeman fires his gun after the match was postponed
Reports on Sunday morning [AEDT] indicated that while South American soccer's governing body (CONMEBOL) had wanted the match to go ahead with a delayed kick-off time, River Plate and Boca Juniors came to a "gentlemen's agreement" not to play on the night.
The full document read: "I'm writing to you to inform about today's incidents in which Boca players suffered superficial skin injuries to their arms, legs, face and torso, with two players [those sent to hospital] reportedly suffering eye injuries which our medical team has not been able to confirm".
Dominguez met with club directors and FIFA President Gianni Infantino.
The rivalry is one of the biggest in football - with both sides originating from the La Boca neighbourhood before River relocated to a different district of Buenos Aires. However, it does now seem likely that the match will be suspended and take place at a later date. Argentina has a deep problem of fan violence - hence the ban on away supporters from this final - and, seemingly, a lack of political will to get to grips with it. Boca and River drew the first leg 2-2 on November 11.
Later, his ambulance was surrounded by River Plate fans as he left the hospital.
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