Islamic State is claiming responsibility for Sunday's suicide bombing at Cairo's Coptic Orthodox Church that killed at least 25 people.
The terror group warned of more attacks in its online statement Tuesday, promising to continue its war against "every infidel and apostate in Egypt and elsewhere."
Television footage shows the suspect walking through the church gates before blowing himself up.
Islamic State identifies him as Abu Abdullah al-Masri which appears to be an assumed name. On Monday, Egyptian President Abdel-Fattah el-Sissi identified the bomber as 22-year-old Mahmoud Shafiq Mohammed Mustafa.
Egyptian authorities have arrested four people allegedly tied to the blast and are searching for others.
Copts make up 10 percent of Egypt's population, but have been a target of anti-Christian violence that followed the overthrow of pro-Islamic president Mohamed Morsi in 2013.