Pope Francis, who is due to visit Egypt this month, on Sunday condemned the blast that killed at least 21 people and injured 50 a Coptic church in the Nile Delta.
"I pray for the dead and the victims. May the Lord convert the hearts of people who sow terror, violence and death and even the hearts of those who produce and traffic in weapons," he said at the end of his Palm Sunday Mass before tens of thousands of people in St. Peter's Square.
He expressed his "deepest condolences" to all Egyptians and to the head of the Coptic Church, who is due to be one of his hosts on the April 28-29 trip.
The blast was the latest assault on a religious minority that has increasingly been targeted by Islamist militants.