A total of 31 people who were injured during the deadly suicide bombing at Alexandria's St Mark's Cathedral on Palm Sunday have returned home from hospital after receiving treatment, Ahram Arabic website quoted Alexandria's governor as saying.

The attack left 17 people dead and 48 injured, of whom 17 remain hospitalised, Governor Mohamed Sultan added.

A state of emergency, according to Sultan, has been declared in all hospitals housing the bombing victims until they recuperate.

On Palm Sunday this week, two suicide bombings hit St George's Cathedral in Tanta and St Mark's Cathedral in Alexandria, killing 46 and injuring dozens in the deadliest attack on Copts in the country's recent memory. 

The Islamic State group claimed responsibility for the attacks, naming the Alexandria suicide bomber as Aba Isaac Al-Masry (Aba Isaac the Egyptian) and the Tanta suicide bomber as Aba Al-Baraa Al-Masry (Aba Al-Baraa the Egyptian). 

A three-month state of emergency was declared later on Sunday by President Abdel-Fattah El-Sisi.

The cabinet approved the state of emergency on Monday, and the parliament approved the decision unanimously on Tuesday.

Copts, who make up about one tenth of Egypt's population of more than 92 million and who will celebrate Easter next weekend, have been targeted by several terrorist attacks in recent months.

In December, a suicide bombing claimed by IS killed 29 worshippers at a Cairo church.

In recent years, Egypt's security forces have been battling a militant insurgency in North Sinai, mostly led by an IS affiliate called Ansar Beit Al-Maqdis, which has killed hundreds of security forces. The group has also claimed responsibility for several attacks in other parts of the country, including the capital.

Security forces say they have killed hundreds of militants in recent years.

Last March, the army said a prominent leader of Ansar Beit Al-Maqdis had been killed in a raid in North Sinai.