President Abdel Fattah El-Sisi of Egypt announced national mourning for 3 days after 21 national border guards were murdered on Saturday. The incident prompted the president to hold meetings with his minister to discuss the national security threats.
The killings took place along the border with Libya in the largest assault that has targeted security forces in many years.
The attack occurred in Wadi Al-Gadidi a desert area about 630 km from Cairo. Another four soldiers were left wounded in the attack, said a military statement on Sunday.
The statement added that the patrol agents had been killed by terrorists that fired one of their rocket propelled grenades during an exchange of fire resulting in a weapons depot being blown up in Farafra a local town killing the border soldiers.
Since the ouster by the army of Islamist President Mohammed Morsi on July 3, 2013, attacks on troops and policemen have been stepped up by militants.
Since that time, the army has had a tough time in defeating the Islamist insurgency, with many based in the Sinai Peninsula, that have killed hundreds in shootings and bombings.
President el-Sisi met late on Saturday with the National Defense Council for discussions involving the domestic and foreign threats to the national security of Egypt.
The president wants to address the efforts in counterterrorism. The council vowed it would avenge the murders of the patrol agents.
The Egyptian army said the attack occurred during fasting in mid afternoon during Ramadan. Political and religious figures condemned the attack as treacherous and vile.
Three assailants were killed in the attack. The area near the Libya bordered has seen great unrest since the 2011 unrest that toppled Muammar Gaddafi, the autocrat, said MENA the state news agency.
Just over one month ago, another five border guards died in a similar form of an assault.
The assault on Saturday came only a week after a soldier and seven civilians were killed in different rocket attacks across the Sinai Peninsula that adjoins Israel and the Palestinian Gaza Strip.