Egypt's Coptic Orthodox Church oversaw the burials late on Sunday of 27 victims of the bomb attack at the Mar Girgis Cathedral in Tanta, Gharbiya governorate, according to state-run news agency MENA.

The victims were buried in the cemetery at Mar Girgis Cathedral, where a bombing, suspected to be a suicide attack, during Palm Sunday service left at least 27 dead and 78 injured.

A few hours later, a second attack in Alexandria killed 17 civilians and police officers, with a suicide bomber blowing himself up outside St. Mark's Coptic Cathedral. The attack happened as the head of the Coptic Orthodox Church, Pope Tawadros II, led the Palm Sunday service inside.

Late on Sunday, following autopsies on the bodies, the General Prosecution authorized the burial of the victims in Tanta and Alexandria.

According to the Coptic Orthodox Church, the victims of the Alexandria bombing will be buried on Monday at the Mar Mina Monastery in Mariut, Alexandria.

The Coptic Orthodox Church does not hold public funeral masses during Holy Week in the run-up to Easter, but funerals and burials are allowed without a mass.

The Islamic State militant group claimed responsibility for both attacks in a statement published on Sunday, saying they were conducted by two of the group's suicide bombers and vowing more attacks against Christians.

Late on Sunday, Egyptian President Abdel-Fattah El-Sisi declared that a nationwide state of emergency would come into effect "once legal and constitutional measures are completed.

Correction: Death toll in Alexandria was revised to 17 instead of 18 following official confirmation