Bishop Angaelos spoke with Premier after the blast struck a chapel close to the outer wall of St Mark's Cathedral in Cairo, leaving another 35 people wounded.
His Grace said: "This was really an inhumane attack that was targeting very proactively and knowingly families - men, women, children, the elderly, the disabled - just a broad spectrum of people who really just wanted to go and pray."
The bombing on Sunday morning bears the hallmarks of Islamic militants opposed to Egypt's President Abdel-Fattah el-Sisi, however, there was no immediate claim for responsibility.
It is the second deadly attack to hit Cairo in recent days, and comes two days after six policemen died in a bomb attack claimed by a group thought to be linked with the outlawed Muslim Brotherhood.
Bishop Angaelos went on to call for a "thorough investigation", adding : "Our main concern at the moment is pastorally to the families who have losted loved ones and this will have broken families apart.
"It's not unimaginable that families who have gone to church on a Sunday will have lost some of their members, and some will have survived - maybe injured."