Two powerful blasts triggered by Islamic State in two churches packed with worshippers celebrating Palm Sunday in Egypt's Tanta and Alexandria cities.
The Egyptian government has ordered military special forces to assist the police in securing vital state facilities across the country.
The Islamic State released a five-minute video on Sunday purportedly showing the beheading of 21 Egyptian Christians that they captured in Libya.
Daring the military-backed government, supporters of deposed Egyptian President Mohammed Morsi have called for a "million person march" tomorrow against his ouster, even as police today arrested two top leaders of an Islamist party in a widening crackdown on protesters.