A stunned nation watched funerals for victims of the bombings on national TV and citizens raised questions and fears about what some consider lax security at churches.
"The state of emergency means absolutely nothing to me," said Andrew Abdel Shaheed, an Egyptian Copt in Brussels.
"It means that people will get trailed for no reason and arrested with no warrants, but what does it do for the future of Egyptians? I personally do not feel safe to return to Egypt."
The Sunday strikes, which targeted Egypt's persecuted and vulnerable Christian minority on the first day of the faith's Holy Week leading up to Easter, left at least 45 dead, Egypt's health ministry said Monday.
At least 28 people died in a bomb blast inside a church in the northern city of Tanta, according to the ministry.
In Alexandria, 17 people -- including civilians and police officers -- were killed when a suicide bomber blew himself up outside a Coptic church, the ministry said. At least 125 people were injured in the attacks.
The Cabinet will allocate 100,000 Egyptian pounds ($5,530) compensation to families of each victim in Tanta and Alexandria's church bombings, state TV said.
ISIS, which claimed responsibility, warned of more attacks in a statement. "The Crusaders and their apostate followers must be aware that the bill between us and them is very large, and they will be paying it like a river of blood from their sons, if God is willing," the group said in Arabic.
After the bombings, Egyptian President Abdel Fattah el-Sisi declared a period of mourning. The government formed a council to counter terror and extremism.
"The attack will not undermine the resolve and true will of the Egyptian people to counter the forces of evil," the President said in a statement. The Egyptian Cabinet, on its website Monday, said it had approved a three-month, nationwide state of emergency that went into effect at 1 p.m. Cairo time (7 a.m. ET).
"The state of emergency allows both the armed forces and the police to execute those procedures necessary to combat the threats of terrorism and its financing, maintain security around the country and protect public and private property, as well as preserving the lives of citizens," the statement said.
The country's parliament must now approve the move within seven days for the three-month initiative to remain in effect. The vote had been set for Monday but has been postponed until Tuesday. The parliament, expected to approve the decision, wants Prime Minister Sherif Ismail to explain the reasons for the move.
In a statement issued on the Telegram messaging platform and circulated by several ISIS supporters, the militant group identified the bombers as Egyptian nationals. Egyptian authorities have not confirmed the bombers' nationalities.
How the attacks unfolded
The first blast ripped through a Palm Sunday service at St. George's Church in Tanta. An explosive device had been planted under a seat in the main prayer hall.
News footage from Tanta showed people gathering at the church, singing hymns. The video then quickly switched to bars as harrowing screams and cries echo in the background.
Victoria Michell, whose father was killed in the attack, described a scene of horror when the explosive detonated.
"A lady next to me lost her eye. Other people were cut to pieces; blood and body parts were everywhere. The choir was also dead on the floor. The chandelier above me crashed to the floor," she said.
Not long afterward, a suicide bomber attacked outside St. Mark's Coptic Orthodox Cathedral in Alexandria, according to state news outlets.
Police officers who had been posted outside the church stopped a man wearing an explosive belt from entering the church, the Interior Ministry said. Two of those officers, a man and a woman, were killed, along with civilians and other police staff.
'Security is very weak'
After the attack in Tanta, authorities replaced the provincial police chief amid anger and frustration over the attacks. Citizens in Tanta told CNN they believe security is poor and demanded it be changed. They say church security guards are ineffectual.
"Security is very weak and they are falling short of their duty. How can someone plant an explosive inside the church? Why didn't they search him?" said Amel Roushdi, who is Christian.
"We don't know the old security chief and we won't know the new one," she said.
Despite the violence, she said she won't be intimidated.
"I will not abandon the church. We are a generation that won't leave the church or Egypt."
Mo'men Ahmed Fouad, a 17-year-old Muslim, had been near the church in Tanta when he heard a loud blast. He later entered the sanctuary and saw a scene of devastation.
"I don't feel secure at all. Muslims and Christians have always lived together and coexisted. I would like security to be intensified," he told CNN. "How could someone enter a church to do this?"
In Alexandria, caskets arrived at a collective funeral in the Marmina (St. Mina) Monastery on the outskirts of the city. "They are martyrs," mourners said. "They are with God now."
A persecuted minority
Copts in Egypt have faced persecution and discrimination that has spiked since the toppling of Hosni Mubarak's regime in 2011
. Dozens have been killed in sectarian violence. In December, an attack at a Coptic church
in Cairo killed 25 people.
Coptic churches and homes have been set on fire, members of the Coptic minority have been physically attacked, and their property has been looted, rights group Amnesty International reported in March.
Coptic Christians make up about 10% of Egypt's population of 91 million. They base their theology on the teachings of the apostle Mark, who introduced Christianity to Egypt. Tanta is roughly 60 miles (96 kilometers) north of Cairo, in the Nile delta.
Pope Francis is scheduled to visit Cairo this month
. He will meet with various religious leaders, including the head of the Coptic Orthodox Church. Along with others, the Pope expressed his grief after the church attack.
The White House
said Monday that Trump spoke to Sisi on Sunday and conveyed "his deepest condolences to Egypt and to the families who lost loved ones in the heinous terrorist attacks against Christian churches on Palm Sunday." Trump also "expressed his confidence" in Sisi's "commitment to protect Christians and all Egyptians."