It was the deadliest incident of soccer violence since Oct. 16, 1996, when at least 78 people died and 180 others were injured in a stampede at a stadium in Guatemala City before a World Cup qualifying match between Guatemala and Costa Rica.
The Port Said game was a face-off between two teams with a long history of fierce competition, Al-Masry, the home team, and Al-Ahly, a record 36-time winner of the Egyptian league and a six-time winner of the African Champions League.
FIFA President Sepp Blatter said he was "shocked and saddened" by the deaths.
"This is a black day for football. Such a catastrophic situation is unimaginable and should not happen," he said in a statement.
The Confederation of African Football, which organizes the African Cup, said a minute's silence would be held before all quarterfinals this weekend as a mark of respect for the dead.
CAF President Issa Hayatou said, "African football is in a state of mourning."
Associated Press writers Ben Hubbard and Maggie Michael in Cairo and Gerald Imray in Franceville, Gabon contributed to this report.