Boca Juniors out of 2015 Copa Libertadores after chemical attack on River Plate team

One of South America's most famous clubs, Boca Juniors, was thrown out of the continent's most important club tournament on Sunday following an attack by its fans on players from rivals River Plate.

Referee Dario Herrera had to be escorted from the pitch by riot police after he called off the Copa Libertadores game between Boca Juniors and River Plate. Reuters/Enrique Marcarian

Boca Juniors were thrown out of the Copa Libertadores on Sunday as a punishment for a chemical liquid attack on players from River Plate.

South American football's governing body (Conmebol) fined the club 175,000 euros and barred spectators from the next four home matches.

The judgement was handed down following an incident in which toxic liquids were thrown at players from arch-rivals River Plate during the second leg of a last 16 Copa Libertadores tie.

The game was called off after 45 minutes with the score at 0-0.

River Plate, who had won the first leg 1-0, will advance to the last eight of South America's most prestigious club competition.

"Conmebol's disciplinary commission has decided to exclude Boca Juniors from the 2015 Copa Libertadores," said a statement from the governing body.

River Plate players were returning for the second half when a chemical irritant was put into the inflatable tunnel leading from the dressing rooms to the pitch.

The attack left several players rubbing their eyes in agony as teammates threw water in their faces to try to relieve the pain.

Doctors said four players suffered inflammation of the cornea after the incident in Thursday's match and would need a few days to recover from their injuries.

Media reports initially said the substance was pepper spray but Boca president Daniel Angelici said that was incorrect. "It wasn't pepper spray, it was a toxic liquid," he said.

Television images showed a Boca fan with his face covered, apparently introducing something into the inflatable tunnel from the seating area behind it.

Prosecutors are investigating the incident from the footage. They have also analysed the shirts of the injured players to identify the substance.

Boca's stadium, the Bombonera, was closed on Friday morning after the attack.

Football in Argentina has been marred by violence. In December footballer Franco Nieto, 33, died after being struck on the head following a match between regional club Tiro Federal and Chacarita Juniors.

Commentators said that Thursday's incident was a nadir for the sport in the country.

"If there was any dignity left in Argentine football, it was torn to shreds at the Bombonera," said an editorial in newspaper Pagina/12. "Football and its leadership have hit bottom."