|Violent protests by Christians against the church bombing underlined Egypt's simmering religious tensions [Reuters]
Clashes have flared in the northern Egyptian city of Alexandria, following a car bombing outside a Coptic Christian church that killed 21 and wounded 97 people.
Police and Christian men faced off late on Saturday afternoon, with reports of rubber-coated bullets and tear gas being fired at crowds of young men.
Reporting for Al Jazeera, Nadia Abou El-Meg, a journalist in Alexandria, said: "This scene [of clashes] has been [witnessed] several times today. The protesters started gathering and throwing stones ... the police responded with tear gas.
"Tension is running very high and people are very angry ... We saw a lot of people weeping and screaming and asking why are they being attacked.
"The church has issued a statement which was also very angry, demanding justice, and criticising the performance of the government.
"More and more people are gathering as the night is falling. Many people are not buying this idea of the suicide bomber."
The Copts are the biggest Christian community in the Middle East and account for up to 10 per cent of Egypt's 80m population.
No bombing claim
There was no immediate claim of responsibility for Saturday's bombing, which came as nearly 1,000 faithful left al-Qiddissine church, located in Alexandria's Sidi Bechr district.
According to the Egyptian interior ministry, the car that exploded was parked in front of the church.
After the blast occurred early on Saturday morning, enraged Christians emerging from al-Qiddissine church fought with police and stormed a nearby mosque.
Al Jazeera's Ayman Mohyeldin, reporting from the Egyptian capital Cairo, said that the car bomb probably involved sophisticated remote-control timer technology.
"Churches in Egypt are heavily guarded, so undoubtedly questions will arise about how a car was parked so close to the church and who was able to detonate it from a distance," he said.
While it was not known who was responsible for the blast, a group calling itself al-Qaeda in Iraq had threatened the country's Coptic Christian community.
The Egyptian interior ministry blamed the bombing on "foreign elements".
Adel Labib, Alexandria's governor, has linked the attack to al-Qaida, but our correspondent says the government has not made clear who they were blaming for the bombing.
Plea for protection
The attack in Egypt prompted Pope Benedict XVI in the Vatican to call for Christians throughout the Middle East to be protected.
The bombing comes almost two months to the day after an October 31 attack by Muslim fighters on Our Lady of Salvation church in central Baghdad, which left 44 worshippers, two priests and seven security forces members dead.
Al-Qaeda's Iraqi affiliate claimed responsibility for that attack and made new threats against Christians.
The group threatened to attack Egyptian Copts if their church did not free two Christians it said had been "imprisoned in their monasteries" for having converted to Islam.
The two women were Camilia Chehata and Wafa Constantine, the wives of Coptic priests whose claimed conversion caused a stir in Egypt.
Protection around Copt places of worship was discreetly stepped up after the threats, as Hosni Mubarak, the Egyptian president, said he was committed to protecting the Christians "faced with the forces of terrorism and extremism".
Egypt's Coptic Christians often complain of discrimination and have been the target of religious violence.
In 2006 a man attacked worshippers in three churches in Alexandria, killing one person and wounding others.
Authorities said at the time he had "psychiatric problems" but this was rejected by the Coptic community.
Clashes broke out between Copts and Muslims the following day at the funeral of the victim, with one person killed and several wounded.
In November clashes took place in a southwestern neighbourhood of Cairo between Coptic demonstrators and police after local authorities refused to allow a community centre to be transformed into a church.
Two Christians died and dozens were wounded.
Source: Al Jazeera and agencies