The Copa Libertadores second-leg game between Santos of Brazil and Independiente of Argentina was abandoned after police clashed with the home crowd - who had been told only 12 hours before kick-off that rather than being level on aggregate they were actually 3-0 down.
Santos fans at the Pacaembu Stadium in Sao Paulo began throwing missiles at the Independiente bench and on to the pitch with eight minutes of the game to go, and the score 0-0 on the night.
Many others then stormed the perimeter fence, where police used batons to beat them back.
Police then used percussion grenades as some fans climbed over the barriers to get on to the pitch.
About 45,000 Santos fans had bought tickets to the game in hopes of a victory in South America's top club competition after they drew the first leg in Buenos Aires 0-0.
But 12 hours before the game started, officials at Conmebol - the organisation that runs football on the continent - changed that result to a 3-0 win to Independiente.
It made the decision after its records revealed Santos' Uruguay international Carlos Sanchez had not served the entirety of a ban in the competition handed out three years before, when he got a red card while playing for River Plate.
Santos pointed out they had checked Conmebol's own online system beforehand and it had revealed no outstanding bans.
Although Santos appealed, the 3-0 result was upheld. With the second game abandoned with no change in that overall score, Independiente qualified for the quarter-finals.
Independiente left the pitch with eight minutes of the game remaining
Fernando Duarte, BBC Brazilian football pundit
Even for Conmebol, this is a new low.
It beggars belief that this penalty was decided only hours before the game.
Leadership in South American football has been severely weakened since the 2015 Fifa scandal, which brought down so many of the leaders at the top of football in the continent.
Even though there's not much the clubs can do, they will be enormously angered.
Sao Paulo is the richest and most powerful state in Brazil - fans there will be absolutely foaming at the mouth. This is the club at which Pele made his name; Neymar started there too.
Brazilian clubs have often felt that Conmebol is against them - and this will have energised them.
If they were a bit more united, this could tip them towards formally opposing Conmebol.