Egypt's President Abdel Fattah al-Sisi has ordered military troops be deployed across the country after nearly 50 people were killed in bomb attacks on two churches.
At least 44 people have been killed in bomb attacks on two Egyptian Coptic churches on Palm Sunday that included the seat of the Coptic Pope.
Islamic State claimed responsibility for the attacks, which also injured more than 100 people and occurred a week before Coptic Easter, with Pope Francis scheduled to visit Egypt later this month.
The first bombing, in Tanta, a Nile Delta city about 100 km north of Cairo, tore through the inside of St. George Church during its Palm Sunday service, killing at least 27 people and injuring at least 78, the Ministry of Health said.
The second, carried out a few hours later by a suicide bomber in Alexandria, hit Saint Mark's Cathedral, the historic seat of the Coptic Pope, killing 17 people, including three police officers, and injuring 48, the ministry added.
Coptic Pope Tawadros, who had attended mass at Saint Mark's Cathedral, was still in the building at the time of the explosion but was not harmed, the Interior Ministry said.
Thousands gathered outside the Tanta church shortly after the blast, some weeping and wearing black.
They described a scene of carnage. "There was blood all over the floor and body parts scattered," said a Christian woman who was inside the church at the time of the attack.
Islamic State's branch in Egypt appears to be stepping up attacks and threats against Christians, who comprise about 10 per cent of Egypt's 90 million people and amount to the biggest Christian minority in the Middle East.
Though Copts have in the past faced attacks by Muslim neighbours, who have burnt their homes and churches in poor rural areas, the Christian community has felt increasingly insecure since Islamic State spread through Iraq and Syria in 2014 and ruthlessly going after religious minorities.