Egypt's Coptic Pope Tawadros II has called on Egyptians to listen to the state warnings and not to travel to Libya.
During the holy mass on Tuesday, Tawadros extended condolences to the families of 21 Coptic Christian men, who were brazenly slaughtered by the Islamic State militant group.
"We offer condolences to the families and we congratulate them too," Tawadros said, for the wreath of glory the slain are believed to have in heaven, according to the Christian Orthodox faith.
A graphic video released on Sunday showed the beheading of the men who were kidnapped several weeks earlier while working in Libya. The killing provoked public anger and prompted Egypt to launch air strikes against the Islamic State group's posts in Libya.
Hours after the military announcement, Egypt's President Abdel-Fattah El-Sisi visited Tawadros in the Cathedral to extend condolences for the victims.