The "extremists" were killed in two separate incidents in the middle Sinai, but the military did not say when they took place.
Both involved the air force and "law enforcement forces".
The military said a planned "hostile act" was foiled after "a highly dangerous terrorist" group was discovered and tracked, and six militants were killed in a mountainous area.
In a separate incident, three "highly dangerous" extremists were killed and another was arrested.
Also Read
On Egypt's western border with Libya, warplanes have attacked and destroyed 15 four-wheel-drive vehicles carrying weapons, ammunition and contraband over the past 24 hours, the military said on Sunday.
The air strikes took place following intelligence that "criminal subjects were gathering to sneak into Egypt", it said.
The military has boosted its operations on the border, repeatedly expressing concern about militants crossing the frontier to launch attacks.
Libya has been wracked by chaos since the 2011 uprising that toppled and killed longtime dictator Moamer Kadhafi, with rival authorities and militias battling for control of the oil-rich country.
The same month, the air force attacked "terror camps" in Libya in retaliation for a deadly attack on Coptic Christians in Egypt, saying the assailants had been trained there.
Egypt's military is battling a local affiliate of IS which has waged a deadly insurgency in the northern Sinai that has killed hundreds of members of the security forces.
Since December, IS has also targeted Christians in other parts of the country, including in Cairo, killing dozens.
Disclaimer: No Business Standard Journalist was involved in creation of this content