Five Egyptian soldiers and 16 extremists were killed early Wednesday when the army was attacked in the Sinai region, the military said, the second such deadly extremist attack in days.
Extremist fighters attacked at dawn, an army spokesman said in a statement.
“One officer and four soldiers were killed and two other soldiers were wounded,” the statement read, adding that seven extremists were killed.
There was no immediate claim of responsibility for Wednesday's attack.
But it came four days after an ambush on the Sinai Peninsula claimed by the ISIS group killed 11 Egyptian soldiers, the military's highest loss of life in years.
The military said Saturday's “terrorist” attack was against a water pumping station.
ISIS claimed responsibility the following day, announcing on its Amaq propaganda site to have seized the weapons of soldiers it killed and to have torched a military post.
Egypt's Sinai Peninsula has been gripped for more than a decade by an armed insurgency, which peaked after the ouster of late Islamist president Mohammed Morsi in 2013.
More than a thousand suspected militants and dozens of security personnel have been killed since the start of operations, according to official figures.