The head of the governing body for world football was gutted to learn about the clashes between rival fans, which resulted in the death of at least 73 people in Africa
At least 73 people have been killed after thousands of Al-Masry supporters invaded the pitch to attack fans and players from the opposing team.
"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," Blatter said in a statement on FIFA's website.
"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."
Egyptian FA president Samir Zaher has announced that the league has been postponed indefinitely as a result of the incident.
Meanwhile, the Confederation of African Football (CAF) has 'expressed shock' at the events in Egypt, with president Issa Hayatou sending a message of condolence to the Egyptian FA.
"African football is in a state of mourning," he said.
A minute's silence will be held during the quarterfinal matches of the 2012 African Cup of Nations at the weekend.