Thousands of Coptic Christians have packed churches across Europe and the Middle East to celebrate Christmas Eve mass amid security fears following a recent deadly bombing at a Coptic church in Egypt.
Security was stepped up across Egypt as threats against specific churches were posted on the internet, days after the New Year's Day bombing of the al-Qiddissin Church in Alexandria that killed 23 people.
Tensions remained high in the country ahead of the Coptic Christmas on Friday as Copts gathered for mass, and the mood was somber outside St Mark's Cathedral in the capital, Cairo.
Al Jazeera's Ayman Mohyeldin, reporting from outside the church, said Egyptian authorities are still trying to identify the attackers.
"The government says it is carrying out an intense search operation to identify just who was behind that attack on the church in Alexandria," he said.
"They also continue to reiterate that the attack was not just aimed at Copts, but all Egyptian citizens."
Solidarity amid tensions
Al-Qaeda in Iraq has been threatening Christians in Iraq and Egypt. In response to threats against the Copts, Egyptian activists called on Muslims to form human shields in front of churches on Christmas Eve.
But Al Jazeera's Zeina Khodr, reporting from Alexandria, said Muslims had been urged by the church not to attend the Christmas Eve Mass.
"The Coptic church here in Alexandria issued a statement yesterday asking Muslims not to attend the Christmas Eve Mass," she said.
"According to that statement they said that they have to take into consideration the feelings and the sensitivities of the relatives of the victims."
Khodr said there was a sense of defiance among the country's Christian population, who would not be frightened away and would continue to pray in churches.
There is also tension and a sense of anger, our correspondent said. "The Christian community is angry; their anger directed at the state," she said.
Human rights groups say Egyptian police have been too slow to punish violence motivated by religion, sending a message that it is unacceptable.
Egypt's Muslims and Christians have co-existed for centuries, with occasional clashes often the result of family or business disputes or cross-faith relationships, rather than ideology.
Christians complain of discrimination in the job market and a lack of representation in government, the army and business.
A perception of growing intolerance is leading some to shun their Muslim compatriots.
Some blame growing tensions on a gradual Islamisation of education promoting a single, Islamic version of Egypt's identity that belies a diverse cultural history.
"Our school books are preaching Islamisation," said Youssef Sidhom, the Christian editor of weekly newspaper Watani.
"Coptic history of Egypt is to a vast extent withdrawn ... The syllabus is using Islam as the source of all traditions and norms."
Some young Copts, usually fiercely loyal to their church leaders, have begun to criticise them for keeping too low a profile and allowing political Islam to influence state policy.
Hosni Mubarak, the Egyptian president, has called for unity after the Alexandria attack, saying the bomber targeted all Egyptians.