The deaths occurred during an ongoing Egyptian operation against militants near the Palestinian territory of Gaza, a military spokesman said, according to state media.
Sinai has fallen into a state of lawlessness since the uprising that toppled Egyptian President Hosni Mubarak last year. Both Israel and the United States have voiced their concern about the rise of terrorist cells in the Sinai.
Soldiers killed 32 suspected terrorists and destroyed 31 tunnels connecting Gaza and Egypt since a military offensive in the region began last month, said spokesman Col. Ahmad Mohamed Ali.
Scores of tunnels have been used for smuggling everyday goods to Palestinian civilians because of Israeli trade strictures. Weaponry has also been smuggled.
Gaza tunnel economy hit by clampdown
Ali said soldiers have seized unmanned drones to be used for attacks. They also confiscated rifles, anti-aircraft machine guns, mortar launchers, artillery ammunition, anti-tank mines, and vehicles. Troops have arrested several dozen people.
Israeli and Egyptian authorities have coordinated to allow the helicopter gunships and heavy machinery into the demilitarized zone in accord with the Camp David agreement signed in 1979.
Ali said the military operations don't breach the treaty. Once called Operation Eagle, now Operation Sinai, the offensive started after more than a dozen Egyptian soldiers were killed and seven others were wounded in an August 5 attack near the Rafah border crossing with Gaza.
The assailants stole two armored vehicles from Egyptian forces and tried to enter Israel.
Egyptian President Mohamed Morsy has visited the Gaza border and vowed to bring justice to those affected. He dismissed several security officials and the governor of North Sinai province in the wake of the attack.
Egypt kills militants, seizes weapons in Sinai offensive
Egyptian forces have killed about 36 people so far in its fight against jihadis in the volatile Sinai peninsula, the army said on