Egyptian President Hosni Mubarak has vowed not to allow terrorists to destabilize his country or divide Christians and Muslims.
The Egyptian leader made the pledge in a televised address following the New Year's Eve attack on the Saints Church, a Coptic church in Alexandria that left at least 21 people dead.
U.S. President Barack Obama described the bombing as a "barbaric and heinous act" and said the United States, a major ally, was ready to help Cairo in responding to it.
Alexandria governor Adel Labib has accused Al-Qaeda of planning the bombing.
Egypt's Christians have been threatened by an Al-Qaeda-linked group that calls itself the Islamic State of Iraq, which attacked a church in Baghdad two months ago.
An Iraqi deputy interior minister, Hussein Kamal, urged Arab states to cooperate in the fight against terrorism and to help stop Arab militants training in Iraq and then returning home.
Dozens of worshipers attended Sunday Mass at the Saints Church while riot police guarded the building outside.
Pope Benedict XVI on January 1 denounced the violence during a summit with religious leaders in Assisi, Italy.
"Yesterday we heard with great pain of the ferocious attack against the Christian Coptic community in Alexandria," Benedict said. "This vile gesture of death, like that of putting bombs near to the houses of Christians in Iraq to force them to leave, offends God and all of humanity, when just yesterday we prayed for peace and started the New Year with hope."
He added: "Facing the threatening tensions of the moment, especially discrimination, injustices and religious intolerance, which today strike Christians in a particular way, once again, I make a pressing appeal not to give in to discouragement and resignation."
compiled from Reuters reports