Universidad de Chile have accused opponents Independiente and the Argentine police of failing to protect their supporters from a “brutal and inhuman beating” that hospitalised 19 of their supporters.
The Copa Sudamericana last-16 match was abandoned on Wednesday following violent clashes in the stands in Buenos Aires.
Violence broke out at half-time when objects including a stun grenade were thrown from the away section on to the bottom tier that contained home supporters.
The match was abandoned in the second half when home fans entered the away section, attacking the visiting supporters and forcing them to flee.
Universidad de Chile say 16 of the 19 supporters hospitalised have been discharged, while a fan in life-threatening condition remains in intensive care but has “significantly improved” after having surgery for a skull fracture.
The Chilean club say the night will be “remembered as one of the most violent chapters in the history of football”.
They allege that Independiente fans “entered the visiting section unhindered” and performed “extremely violent and inhuman acts, impossible to detail in this statement due to their brutality”.
Universidad de Chile have also accused Independiente supporters of attempting to enter the away dressing room to attack their players and said the windows of their bus were smashed.
The club said around 100 of their supporters had been arrested but allege that “not a single attacker” from the home section has been detained.