Shadi al-Menei, the head of a Sinai Peninsula Islamist militant group, was shot dead by unknown assailants, security sources said, days before Egypt holds elections to vote for a new president.
The security sources said al-Menei and five others were killed in a firefight while walking in Maghara in central Sinai.
Al-Menei was the head of Ansar Beit Al Maqdis, or Defenders of Jerusalem, which was responsible for several recent attacks on security forces in Egypt.
A statement on the army spokesman's official Facebook page said the army executed an operation that resulted in the killing of six extremely dangerous criminal elements on Thursday. It did not name Menei and it was not immediately clear if the statement was referring to the same incident.
Separately, one security officer was shot dead by unknown assailants at a security checkpoint in the North Sinai town of Rafah, near the border with Israel, state news agency MENA reported early on Friday.
Islamist militants in the Sinai stepped up their attacks against army and police forces last year after the army ousted Islamist president Mohamed Mursi in July.
The army then launched a major ongoing operation to fight militants in the Sinai.
Egypt is gearing up to hold fresh elections next week, which former army chief and presidential candidate Abdel Fattah al-Sisi, who led Mursi's ouster, is widely expected to win.