The Egyptian military has carried out airstrikes and raids against militants reportedly linked to Friday's Sinai attack that killed at least 305 people. President el-Sissi promised the attack would "not go unpunished."
World leaders condemned Friday's deadly assault on a Sinai mosque, as Egypt hit back with airstrikes on suspected Islamist targets.
The United Nations also condemned the attack in "the strongest terms" and expressed its condolences for the victims' families and the people of Egypt.
Egypt received messages of solidarity and condolence from Israel, Iran, Iraq, Saudi Arabia, and the Vatican.
No group claimed responsibility for the gun and bomb assault. The government blamed the attack on the Sinai affiliates of the "Islamic State" (IS) militia. The group has committed several similar attacks in Egypt's restive northern region in the past, according to authorities.
Some observers, however, believe the attack was primarily motivated by the long and bloody conflict between the local Bedouin tribes and the government in Cairo.
Raids and airstrikes
Egypt's air force on Friday bombed "terrorist" locations in the northern mountainous area around Bir al-Abed in response to the deadliest terror attack in the country's history.
"The air force has over the past few hours eliminated a number of outposts use by terrorist elements," the army said on Friday.
Spokesperson for the Egyptian air force Tamer-el Refai said that air force planes sent to Bir al-Abed had "destroyed several vehicles used in the attack" as well as targeted hideouts where weapons and ammunition were stockpiled.
President Abdel Fattah el-Sissi had promised that the attack would "not go unpunished." He convened an emergency security meeting soon after the terrorist assault.
"The armed forces and the police will avenge our martyrs and restore security and stability with the utmost force," President el-Sissi said in a televised address.
"What is happening is an attempt to stop us from our efforts in the fight against terrorism, to destroy our efforts to stop the terrible criminal plan that aims to destroy what is left of our region," he added.
Violence at prayer time
Authorities said that shortly after the noon prayer time, men in four off-road vehicles surrounded the Al Rawdah mosque, some 40 kilometers (25 miles) west of the provincial capital, Arish, before planting explosives.
After the explosives went off, the attackers opened fire at those who fled. Media reports described at least 20 masked gunmen using automatic rifles in the assault.
The victims included civilians and military conscripts.
The mosque is largely attended by Sufis, who follow a mystical branch of Sunni Islam. Islamic extremists consider Sufis heretics.
Militants have also previously targeted Sufis and Coptic Christians, as well as civilians accused of cooperating with government forces.
Bombs not enough
Commenting on the latest development for DW, German-Egyptian political scientist and expert on jihadism Asien El Difraoui said that the regime in Cairo would benefit from a softer course on the Sinai Peninsula.
One of the problems in the Sinai region, according to the expert, is that Salafists ideas have been widespread for years and served "as a good foundation for the jihadi way of thinking."
"Also, Bedouins in the Sinai were always seen as second-class citizens. They are living under very tough economic conditions and are stereotyped as criminals and smugglers. They don't get anything from the two riches of Sinai, neither from the oil wells nor from the tourism," El Difraoui added.
"Egypt needs to find the way back to dialogue," he told DW's Kersten Knipp. "You can't answer terror with just bombs."