Heavily armed police and undercover agents were deployed in churches across Egypt on Sunday, as authorities tightened security and detained hundreds of suspects after a suicide bombing outside a church in the port city of Alexandria, killed 21 people and injured nearly 100.
The Interior Ministry deployed heavily armed police as well as undercover agents and checkpoints were set up outside all provinces and cars were being prevented from parking near churches, the local media reported.
State run media reported that hundreds of suspects were detained in the south of the country, without giving further details.
Shortly after midnight on Friday, a suicide bomber detonated his nail packed bomb outside the Coptic Christian Church of the Saints in Alexandria where hundreds were attending a New Year's Eve service.
According to the Health Ministry, 21 people were killed and 97 injured in the blast which sparked religious clashes between Christians and Muslims. Angry Christian protesters clashed with police and Muslims.
Meanwhile, Christians prayed on Sunday at the church targeted by the bomber, whom President Hosni Mubarak described as part of international "terrorism".
Bloodstains from the attack were still visible on the facade of the church.
Mubarak accused "foreign hands" of carrying out the deadly attack.
Schools and universities observed a minute's silence for the victims on Sunday.
The Education Ministry issued guidelines to school teachers to talk about national unity and convey the government's stance that church bombing was 'a terrorist attack and not sectarian'.
No one has so far claimed responsibility for the attack on the church, which belongs to the Oriental Orthodox family of churches, but a group calling itself 'Al Qaeda in Iraq' has vowed to attack churches in Egypt.
The group threatened to attack Egyptian Copts if their church did not free two Christian women, who it alleged had been "imprisoned in their monasteries" for having converted to Islam.
The gropu is also responsible for an earlier kidnapping of Christian worshippers in the Church of Lady of Salvation in the Iraqi capital of Baghdad. The Copts are the largest Christian community in the Middle East, accounting for up to 10% of Egypt's 80 million population.