At least 11 Egyptian troops, including an officer, were killed Saturday in a militant attack on a water pumping station east of the Suez Canal, the military said.
In a statement, it said at least five other troops were wounded in the attack, one of the deadliest against Egyptian security forces in recent years.
Troops thwarted the attacks and were pursuing militants in an isolated area of the northern Sinai Peninsula, the statement added. It gave no further details or the attack's precise location.
President Abdel Fattah el-Sissi mourned the death of the troops, vowing in a Facebook post to the continue fighting the militants and “uprooting terrorism.”
Two Northern Sinai residents said the attack took place in the town of Qantara in the province of Ismailia, which stretches eastwards from the Suez Canal.
The militants ambushed troops guarding the pumping facility, before fleeing to the desert in Northern Sinai, according to the residents who spoke on condition of anonymity for their safety.
No group claimed responsibility for Saturday's attack.
Last week, suspected militants blew up a natural gas pipeline in Northern Sinai's town of Bir al-Abd, causing a fire but no casualties.
Egypt is battling an Islamic State-led insurgency in the Sinai that intensified after the military overthrew an elected but divisive Islamist president in 2013.
The militants have carried out scores of attacks, mainly targeting security forces and Christians.
The military has claimed that insurgents have suffered heavy losses in recent months as security forces, aided by armed tribesmen, intensified their efforts to eliminate them.
The pace of militant attacks in Sinai's main theater of operations and elsewhere has slowed to a trickle since February 2018, when the military launched a massive operation in Sinai as well as parts of the Nile Delta and deserts along the country's western border with Libya.
The fight against militants in Sinai has largely taken place hidden from the public eye, with journalists, non-residents and outside observers barred from the area.
The conflict has also been kept at a distance from tourist resorts at the southern end of the peninsula.