Eight Egyptian soldiers and 14 militants are reported to have been killed in fighting in central Sinai on April 14.
An army statement said the militants, some carrying explosive belts and grenades, attacked a military checkpoint at around dawn.
Four of them detonated their explosive belts, killing the soldiers and wounding 15 others, the army statement added.
The attack was the largest against Egyptian security forces since President Abdel el-Sisi won a second term in office last month.
It also came just hours after the country extended a state of emergency imposed last year.