Egypt's President Abdel-Fattah El-Sisi said he will impose a state of emergency countrywide for three months, following attacks on churches in Tanta and Alexandria on Sunday.
In a televised address, he said that the state of emergency will come into effect "once legal and constitutional measures are completed."
"This is only to protect our country … and prevent any targeting of its capabilities," Sisi said.
He also announced the establishment of a new body, the Supreme Council to Combat Terrorism and Extremism, which will be provided with wide-ranging authority according to laws yet-to-be issued.
The council will be responsible for adjusting all aspects of amending religious discourse and facing extremist ideas in the country, the president said.
The Egyptian president addressed the nation on Sunday night after 48 people were killed in twin attacks that targeted churches in Alexandria and Tanta that morning.
Shortly after a meeting of the national defence council which he presided over, Sisi declared a three-month state of emergency would be imposed "upon completion of constitutional procedures".
"I will never say those killed were Christian; they are Egyptians. Remember in July 2013, I requested an authorisation to face possible violence and terrorism, I was talking then about a longtime war," the president said, citing his speech as defence minister and army head following the ouster of former president Mohamed Morsi in 2013.
"Our condolences to all the Egyptian people, I will not say our Christian brothers, our condolences to all Egyptians.
"What is happening now is another attempt to destroy our country; there were economic decisions, terrorist attacks, other acts of hostility against you and you still hold up," Sisi added, addressing the people of Egypt.
He also called on the international community to punish countries supporting and aiding terrorism.
"These terrorist attacks have been targeting all elements of the Egyptian state, including the army, police judiciary, but you, the Egyptian people, did a great job in face of this fascist terrorism, we must remember that, and never let anything disrupt our social fabric."
Sisi, who spoke in a solemn tone, also said that the attacks are in response to recent military successes against terrorism in Sinai.
"We succeeded in Sinai, they [terrorists] hit in another region, we will target in them in that region, they will hit in another one, that is the reality of war against terrorism, but I say to Egyptians to hold up, resist, and we are capable of facing challenges, defeating evil and terrorism and continuing building our country".
Addressing the Egyptian media, Sisi urged all outlets to be "credible, responsible, and aware" when covering news and images related to such incidents and bear in mind not to hurt the feelings of the victims by broadcasting their deceased relatives' images "all day long".
At the end of his speech, Sisi urged the security apparatus in the country to find and bring those responsible for the attacks to justice as soon as possible.