Coptic Christians turned out in their thousands to mourn as news broke that Egypt's Coptic Christian Pope Shenouda III had died.
The 88-year-old's political advisor told Reuters he had died from old age.
Bells tolled in the Abbasiya district of Cairo, site of Egypt's main Coptic cathedral, as word spread.
Shenouda became the 117th Pope of Alexandria in 1971 and was popular with Christians and Muslims alike during his four decades in power.
His criticism of the government's handling of an Islamic insurgency during the 1970s in which Christians were targets, and his rejection of Egypt's peace treaty with Israel, landed him in trouble with the country's then-president Anwar Sadat.
During the rule of Hosni Mubarak he was portrayed in state media as a symbol of religious harmony despite occasional outbreaks of sectarian violence.
His successor will play a crucial role in forging the church's position in the country after the overthrow of Mubarak last year.
