FIFA president Sepp Blatter was left 'shocked and saddened' after violent clashes in Egypt on Wednesday night left many dead.
The Egyptian Football Federation have announced an indefinite suspension of all leagues in the country following the trouble in Port Said, when rival fans invaded the pitch and fought after Al Masry recorded a surprise 3-1 win over Al-Ahly.
Blatter issued a statement to express his sympathy for the families of the victims. It said: "I am very shocked and saddened to learn this evening that a large number of football supporters have died or been injured following a match in Port Said, Egypt."
Reports say at least 73 people have died in the unrest while up to a thousand others are injured after the violence quickly spread.
The statement continued: "My thoughts are with the families of those who have lost their lives this evening.
"This is a black day for football. Such a catastrophic situation is unimaginable and should not happen."
The Egyptian federation issued two statements, announcing a period of mourning and a suspension of football in the country.
"The Egyptian federation has decided to stop the football leagues in all four divisions for an indefinite period after the violence that occurred in the game between Al Masry and Al-Ahly, which represented a tragic shock to the centre of sport in general and the football family in particular," one statement said.
The other added: "The federation has announced that Egyptian football will be in mourning for three days for the souls of those who have fallen victim to the violence that occurred in the wake of the Al Masry-Al-Ahly match."