CAIRO, Jan 26 (Reuters) - A policeman was shot dead outside a prison in Egypt's Port Said on Saturday after protesters gathered at the site where many of the defendants in a fatal soccer disaster case were held, a security source reported.

State media had earlier reported gunshots outside the prison after a court ruled that 21 of the 73 defendants accused of involvement in the Port Said soccer disaster, in which 74 people were killed, were sentenced to death. Soccer fans and families in Cairo had cheered the ruling.

(Reporting by Yasmine Saleh; Writing by Edmund Blair; Editing by Janet L