Port Said's head of hospitals, Abdel Rahman Farag, told Reuters an 18-year-old man and three other people died from gunshot wounds on Sunday.
More than 429 people suffered from teargas inhalation, while 38 were wounded by gunshots, he said.
Wherever there is division in Egypt right now – death seems sure to follow. The greatest toll came amid gunfire and tear gas in Port Said.
Riots sparked by death sentences passed in connection with last year's deadly riot at the Port Said football stadium have killed 22 people.