With the score at 2-1, Stade de Mbour and US Ouakam fans clashed in the second half of extra time.
Among the injured in Saturday’s chaos was the president of the stadium, Mbaye Dia, who was set upon by a group of attackers, said police spokesman Aliou Thiam.
Dia was taken to hospital in a serious condition.
Police used tear gas to keep rioting fans apart.
As spectators tried to flee the stadium, part of the stands collapsed.