The IS group has claimed responsibilty for the bombing at the St. Mark's Coptic Orthodox Cathedral in the Egyptian capital, Cairo, last Sunday.
A statement issued on SITE intelligence group on Tuesday said it was a suicide operation claiming it have killed and wounded 80 "crusaders".
The statement also read that the attack was carried out by Abu Abdallah El-Masri who detonated a suicide belt.
At least 24 people were killed and 49 injured after an explosion inside a church attached to the Coptic Cathedral in Cairo's Abbassyia district.
On Monday, President Abdel Fattah al-Sisi named the suicide bomber as Mahmoud Shafik Mohamed Mostafa, 22, during a funeral for the victims.
Sisi added that four suspects had been arrested, including one woman, for alleged involvement in the attack, while two more suspects were being pursued.
The Interior ministry said they had arrested more suspects later and that they are still searching for others.