Egypt's state news agency said gunmen attacked a checkpoint manned by the military police in a suburb north of Cairo on early Saturday, killing six of them, officials said.
Separately, the country's most active militant group said that one of its founding leaders was killed when a bomb he was carrying was set off by a car accident.
Maj. Gen. Mahmoud Yousri, chief of security of Qalubiya province, told MENA that the attackers stormed the checkpoint in Shubra al-Kheima. Health ministry official Zakariya Abed Rabbo said six soldiers died.
Yousri said explosive disposal experts managed to defuse two bombs left behind by the attackers, but the experts detonated a third bomb which they were unable to defuse.
A statement issued by armed forces spokesman, Col. Ahmed Mohammed Ali, said an armed group which belongs to the Muslim Brotherhood "terrorist group" attacked the soldiers after they finished their dawn prayers.
"These cowardly operations will only increase our determination to continue the war against terrorism," he said.
Egyptian authorities say the Brotherhood has orchestrated a series of bomb attacks on police and other targets that followed the overthrow of President Mohammed Morsi, who hails from the Islamist group.
They have produced little evidence open to public scrutiny to bolster these claims, and most have been claimed by a Sinai-based al-Qaida-inspired group, Ansar Beit al-Maqdis or Champions of Jerusalem. The Brotherhood denies the attacks.
In a statement posted early Saturday on militant websites, the Ansar said one of its founding leaders, Tawfiq Mohammed Freij, was killed Tuesday when an accident set off a "heat bomb" he was transporting in his car. It did not say where the accident took place.
It said Freij, also known Abu Abdullah, was one of the founders of the group, who masterminded the group's tactic of blowing up pipelines to stop Egyptian gas supplies to Israel.
It called him the "field commander" of an August 2011 cross-border attack into southern Israel that targeted a bus and other vehicles near the resort city of Eilat, killing eight people.
The statement's wording suggests that Freij moved from either Sinai or Gaza to Cairo or elsewhere in Egypt in early 2013 to supervise the group's operations, including a failed suicide car bomb attack on Interior Minister Mahmoud Ibrahim in Cairo in September 2013.
The statement could not be independently authenticated, but militant groups regularly use the websites to make announcements.