Egypt's President Abdel Fattah el-Sisi says a three-month state of emergency will be imposed after two bomb blasts killed dozens of worshippers in Coptic Christian churches.

The Islamic State of Iraq and the Levant (ISIL, also known as ISIS) armed group claimed responsibility for Sunday's suicide bombings in the Nile Delta cities of Alexandria and Tanta, in which more than 40 people were killed.

"A series of steps will be taken, most importantly, the announcement of a state of emergency for three months after legal and constitution steps are taken," Sisi said in a speech aired on state television.

Sisi, who in 2013 led the overthrow of democratically elected president Mohamed Morsi, leader of the Muslim Brotherhood, announced the measure after a national defence council meeting.

Under Egypt's constitution, the state of emergency must be presented to the House of Representatives for approval within a seven-day period.

The emergency law expands police powers of arrest, surveillance and seizures and can limit freedom of movement.

Egypt declared a state of emergency in the months that followed the military ouster of Morsi. Part of North Sinai, where ISIL's Egyptian affiliate is based, is still under a state of emergency.

Earlier on Sunday, a statement by the presidential office said that Sisi had ordered troops be deployed across the country to help secure "vital facilities".

'Tremendous security lapse'

The bombings were the latest in a series of assaults on Egypt's Christian minority, who make up about 10 percent of the population and have been repeatedly targeted by armed groups.

Samer Shehata, associate professor at the Doha Institute for Graduate Studies, told Al Jazeera the attacks show a "tremendous security lapse" by Egyptian authorities.

READ MORE: Egypt's Coptic Christians flee Sinai after killings

"In the last few months, there has been an increased number of attacks on Egyptian Copts, individually, as well as on churches," Shehata said, adding that the church in Tanta received a threat 10 days ago.

"I do think this represents a lack of seriousness on the part of the state in really securing the Coptic community and places that could potentially be attacked."

Anger, fear

In Tanta, as security forces cordoned off the church, residents who gathered nearby were unable to hide their anger.

Despite the presence of metal detectors, the bomber was apparently able to enter the building without any hindrance.

"How was the bomb able to enter, while police" were outside the church, asked Nagat Assaad, holding back tears.

"What are the detectors for? We don't want their protection," he told the AFP news agency.There were similar scenes in second city Alexandria after the attack there.

Several hours after the attack, a Coptic woman expressed her anger at police blocking access to the church.

"What's the use of closing the street now? You should have done it before the explosion!" she told AFP.

A bombing at Cairo's largest Coptic cathedral killed at least 25 people and wounded 49 in December, many of them women and children.