(CNN) Egypt's President says he will declare a state of emergency after two deadly bombings targeted Coptic Christian churches on Palm Sunday.

ISIS claimed responsibility for the attacks, which were aimed at a vulnerable religious minority on one of the most important days on the Christian calendar.

The death toll rose to at least 49 Monday, state media reported. At least 27 people died in a blast inside a church in the northern city of Tanta, and 78 people were injured, according to Egypt's state-run news agency Al-Ahram. In Alexandria, 18 civilians and four police officers were killed when a suicide bomber blew himself up outside a Coptic church, Al-Ahram said.

Egyptian President Abdel Fattah el-Sisi declared three days of nationwide mourning following the bombings and said a three-month state of emergency would come into force once legal and constitutional measures have been completed.

In response to the attacks, the country will also form a supreme council to counter terrorism and extremism, Sisi said on state television Sunday after an emergency meeting of the country's National Defense Council.

"We have to pay attention because of Egypt and Egypt's future. We know this is a big sacrifice but we are capable of facing it," he said.

"The attack will not undermine the resolve and true will of the Egyptian people to counter the forces of evil, but will only harden their determination to move forward on their trajectory to realize security, stability and comprehensive development," the President said in a statement.

As we grieve the tragic & heartbreaking loss of Egyptian lives, it is still a failed attempt against our unity. #united_on_PalmSunday — Egypt MFA Spokesman (@MfaEgypt) April 9, 2017

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.

ISIS warned of more attacks in its 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.

How the attacks unfolded

Photos: Church bombing in Tanta, Egypt Security personnel survey the scene of a bomb blast at St. George's Church in Tanta, Egypt, on Palm Sunday. Hide Caption 1 of 6 Photos: Church bombing in Tanta, Egypt Members of the congregation mourn inside St. George's. Hide Caption 2 of 6 Photos: Church bombing in Tanta, Egypt A priest looks at the damage inside the church. Hide Caption 3 of 6 Photos: Church bombing in Tanta, Egypt Security personnel bag a cross as evidence. Hide Caption 4 of 6 Photos: Church bombing in Tanta, Egypt Priests sit next to security personnel investigating the scene of the bombing. Hide Caption 5 of 6 Photos: Church bombing in Tanta, Egypt People gather in front of St. George's Church after the bombing. Hide Caption 6 of 6

The bombings came on the Sunday before Easter, the day that marks the start of Holy Week for Christians.

The first blast ripped through a Palm Sunday service at St. George's Church in Tanta, killing at least 27 and wounding 78 others, state TV reported. An explosive device had been planted under a seat in the main prayer hall, it said.

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.

"Everything is destroyed inside the church," said Peter Kamel, who saw the aftermath of the bombing. Its marble pillars were covered with blood, he said.

Kamel said that most of the injured appeared to be priests and members of the choir.

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.

Egyptian blogger Maged Butter said he saw five or six ambulances and bloodstains 100 meters away from the site of the explosion, which happened near the church gate.

He said women were crying and looking for their loved ones and were yelling at police for "not protecting" them.

"Every now and then, I see a person crying -- I think they are Christian -- and they keep saying: 'have you seen my family? Have you seen my family?'" Butter said.

Nile and Masriya TV, Egyptian state outlets, aired black banners in the upper left of their newscasts to signify mourning for the victims of both explosions.

'Bodies and body parts everywhere'

Fadi Sami heard about the Tanta bombing as he sat in the Alexandria cathedral on Sunday. The head of Egypt's Coptic Church, Pope Tawadros II, was leading Palm Sunday prayers.

Though no one announced the Tanta news, Sami said he could hear the sadness in the pope's voice. He left as the pope finished the sermon. Twenty minutes later, a suicide bomber blew himself up at the gate of the church.

"I came back and the area was covered in smoke. The stores around the church were all destroyed," he said. "There were bodies and body parts everywhere, outside and inside the gate. I saw a man put together what was left of his son in a bag."

Women try to reach loved ones after the attack in Alexandria.

Alexandria sits on the Mediterranean and has a large Christian population. Downtown is usually busy but was relatively quiet on Sunday because of the holiday. "Thank God it is a Sunday, and many shops are closed," Butter said.

David Saeed said he was sitting in the last row in the church when the bomb went off.

"We were just singing and suddenly in a blink of (an) eye, smoke, fire everywhere. I didn't realize what's happening until I saw blood and organs of our friends scattered over the ground," Saeed told CNN.

He said he tried to save some of the dying but couldn't. He helped to carry others to ambulances in front of the church, he said.

Hours later Saeed held a bloody T-shirt that belonged to a friend who was killed in the blast.

"I was shocked. But I'm not angry because ... we're used to it ( this kind of violence) here in Egypt," Saeed said.

"Every church in Egypt just prepares for this," he added. "Everyone knows that some time you will get bombed, you will be killed."

A persecuted minority

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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.

International condemnation

United Nations Secretary-General António Guterres condemned the attacks and offered his sympathies to the victims and to the country in a statement through a spokesman.

Guterres "wishes a quick recovery to those injured and hopes that the perpetrators of this horrific terrorist act will be swiftly identified and brought to justice," said the spokesman, Stéphane Dujarric.

The US State Department also issued a rebuke, calling the bombings "barbaric attacks on Christian places of worship."

"The United States will continue to support Egypt's security and stability in its efforts to defeat terrorism," said acting spokesperson Mark Toner.

Rescue workers help a victim of the attack in Alexandria.

The bombings came days after US President Donald Trump welcomed Sisi to Washington and expressed his support for Egypt. Among the topics of mutual concern were terrorism and ISIS. Trump condemned Sunday's attacks on Twitter and said he has "great confidence Sisi will handle the situation properly."

The United States stands firmly with the Egyptian government and people to defeat terrorism. (5/5) — US Embassy Cairo (@USEmbassyCairo) April 9, 2017

Sisi met Saturday with a US congressional delegation led by US Rep. Darrell Issa, the Egyptian government said. The meeting addressed Egypt's counterterrorism efforts and a strategy to fight terror while encouraging religious tolerance and acceptance of others.

On Sunday, President Trump called Sisi from Air Force One to offer his condolences, a senior administration official told CNN.

Egyptians look on in shock inside Mar Girgis church in Tanta.

Pope Francis is scheduled to visit Cairo this month, where he will meet with various religious leaders, including the head of the Coptic Orthodox Church. He expressed his grief after the church attack.

Evil attacks at St George's Tanta Egypt. As we come to Easter pray for victims, the justice of the cross, hope & healing of resurrection — Justin Welby ن (@JustinWelby) April 9, 2017

Archbishop of Canterbury Justin Welby called the attacks "evil" and urged people to pray for the victims. Russia's President Vladimir Putin condemned the attacks and offered his condolences to Sisi, according to Russia's state-run Tass.