The clashes at dawn left 14 militants dead. They were armed with rifles and RPGs, the armed forces said in a statement. The attack comes two months after the launch of a massive operation against militants in Sinai as well as parts of Egypt's Nile Delta and Western Desert, along the porous border with Libya.
There was no immediate claim of responsibility for the attack which bore the hallmarks of the extremist Islamic State group, whose local affiliate is spearheading an Islamic insurgency in Egypt's Sinai Peninsula.
In an earlier statement, the army said security forces killed 27 militants including six in airstrikes part of its offensive in turbulent Sinai region. It also said that troops arrested 114 suspected militants, including 21 wanted criminals.
The figures provided by the military could not be independently verified as media access to the northern Sinai is heavily restricted. Egypt has for years been struggling to contain the Islamic insurgency in the turbulent Sinai region. It has carried out military operations there that, it says, have killed hundreds of militants.
It has also built a buffer zone along the border with Gaza to curb the flow of militants and weapons through a vast tunnel network. The insurgency, however, has shown no signs of abating.