The attack happened in central Sinai area, 40 km from the town of Bir al-Abd, the source noted that the assailants used rifles and automatic weapons, before fleeing the scene.
Other eight were wounded in the attack, he added. The victims have been transferred to El-Arish Hospital.
North Sinai has been experiencing growing wave of anti-security attacks since the army-led ouster of Islamist leader Mohamed Morsi in 2013, which killed hundreds of police and army men.
A Sinai-based militant group loyal to the Islamic State (IS) regional group claimed responsibility for most of attacks.
Intensified Egyptian military raids killed and arrested hundreds of IS-affiliate extremists in North Sinai as part of the country's "anti-terrorism war" declared following Morsi's ouster.