CAIRO, Dec 13 (Aswat Masriya) - Islamic State on Tuesday claimed responsibility for the bombing of St. Peter church in Cairo, which left 25 people dead and dozens injured.

The bombing, which took place on Sunday, hit the church attached to one of Egypt’s most symbolic sites for Copts, St. Mark’s Coptic Cathedral.

The group said in a statement released online that they were behind the attack and vowed, "to continue war against apostates." They identified the suicide bomber who carried out the attack as Abu Abdullah al-Masri.

Egypt's President Abdel Fattah al-Sisi had named the attacker during a state funeral for the victims on Monday as Mahmoud Shafiq Mohammed Mostafa.

Later on Monday, Egypt's interior ministry said that people in connection with Muslim Brotherhood group were behind the bombing.

Egypt is observing three days of mourning following the explosion. 

Militants have stepped up attacks targeting security forces in Egypt, since the ouster of Islamist President Mohamed Mursi in July 2013 after mass protests against his rule.