In pictures | Bloodbath in two Egyptian churches kills 45 on Palm Sunday, ISIS claims responsibility
President Abdel Fattah al-Sisi has announced a state of emergency for three months in the country.
At least 45 people were killed and nearly 120 others injured in powerful blasts triggered by ISIS in two churches packed with worshippers celebrating Palm Sunday in Egypt's Tanta and Alexandria cities, the deadliest attacks on the minority Coptic Christians in recent years.
The first blast took place in the Coptic church of Mar Girgis, also known as St George, in the Nile delta city of Tanta, about 120 kilometres from Cairo, killing 27 people and injuring 78, the Health Ministry said in a statement.
Security sources said the primary investigations suggest that a person put an explosive device inside the church during the Christian prayers celebrating the Palm Sunday. However, others said the attack was carried out by a suicide bomber.
Hours later, a suicide bomber struck the Saint Mark's Coptic Orthodox Cathedral in Alexandria's Manshyia district, police said.
The latest figure puts the combined death toll from the Tanta and Alexandria attacks at 45.
The Islamic State group claimed responsibility for the twin attacks on churches on Palm Sunday, one of the holiest days of the Christian calendar.
"Islamic State squads carried out the attacks on two churches in Tanta and Alexandria," said the group's propaganda news agency 'Amaq' on its social media accounts.
President Abdel Fattah al-Sisi, in a televised statement, announced a "state of emergency for three months" after a meeting of the national defence council.
Meanwhile, security forces dismantled two explosive devices at Sidi Abdel Rahim Mosque in Tanta city. The mosque, which includes a Sufi shrine, is considered the second most important mosque in city, Al-Ahram Arabic reported.
Sisi condemned the attack and said such terrorist acts will not terrify Egyptians.
(With agency inputs)