The Egyptian government has accused "foreign elements" of carrying out the fatal bomb attack on a church in the northern city of Alexandria that killed 22 people and injured 79 Saturday, dpa reported.
The Interior Ministry said the attack on the Coptic Christian Church of the Saints 20 minutes after midnight was a suicide bombing in which the bomber probably died.
Four policemen who had been guarding the church were among the injured in the blast during a New Year's Eve service.
"Foreign elements were behind the planning and implementation of the attack," the ministry said in a statement. Investigation showed that the bomber had used a "locally-made" bomb containing nails.
The attack sparked an angry response from Christians who stoned a nearby mosque, leading to clashes with the police.
The head of Al-Azhar, the country's highest Islamic authority condemned the attack, saying it could not have been carried out by Egyptians.
"It is a foreign crime implemented on Egyptian land," Ahmed al- Tayeb told state television.
Authorities tightened security around churches across the country in the wake of the attack.
Copts meanwhile held demonstrations outside the church in Alexandria.
President Hosny Mubarak has called on Egypt's "Copts and Muslims to stand united against terrorism and those who threatens security, stability and unity of the country."
The Muslim Brotherhood, the country's largest opposition group, condemned the "suspicious" blast, which "targets the sanctity and security of the country."
Qatar, Kuwait and Syria also condemned the attack.
The Islamic State of Iraq, a group affiliated with al-Qaeda, has recently threatened Christians throughout the Middle East, saying that they are legitimate targets.
The group demanded that pressure be put on Egypt's Coptic Church to "release" two Egyptian women, which they said had converted to Islam and were now being forcibly held by the Coptic Church.
Christians account for roughly a tenth of Egypt's population and accuse Egypt's majority Muslim population of discriminating against them.
Although violence between Christian and Muslim populations is considered rare, tensions have been high since an attack on a church in the south of the country about a year ago. Gunmen opened fire on parishioners leaving a church, killing eight Christians and a Muslim policeman who had been guarding the church.
In November, clashes erupted during a protest by Christians against a decision by the authorities to halt construction of a church in a Cairo suburb. One Christian was killed and several injured, while dozens were arrested.