Two deadly church bombings in Alexandria and Tanta killed more than 45 people in April, months after a bombing near Cairo’s Coptic Cathedral killed at least 25.
An Islamic State group flag
Egypt’s Christian minority has come under attack in recent months.
Islamic State claimed responsibility for all three attacks.
Public prosecutor Nabil Sadek said in a statement on Sunday that some of the suspects held leadership positions in Islamic State and formed cells in Cairo and the southern province of Qena to carry out the church attacks.
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Egypt is facing a more than three-year-old insurgency led by Islamic State that intensified after general-turned-President Abdel Fattah al-Sisi led the military in ousting Islamist President Mohamed Mursi in 2013 after mass protests against his rule.
Attacks were largely against security forces in the sparsely populated Sinai Peninsula in the past, but the militant group has spread its violence to the mainland and increasingly targeted Christian civilians in recent months.
