An improvised explosive device detonated early Saturday in North Sinai's Al-Arish, injuring three security personnel, Al-Ahram Arabic website reported.
The device exploded in Al-Midan area, west of Al-Arish, when an army bus was passing by, carrying Central Security Forces members to their camp after vacation.
Two were mildly injured and have already been discharged from hospital while another remains in hospital with intermediate level wounds.
Reinforcements arrived to the scene and cordoned it off, looking for the assailants.
The military has mounted an extensive campaign in the region to crush militant violence that has killed hundreds of police and troops over the past 16 months. Security forces have announced, in turn, that they killed hundreds of militants. The violence has also led to civilian casualties.
Earlier in November, Ansar Beit Al-Maqdis, Egypt's deadliest militant group operating in Sinai, swore allegiance to the jihadist Islamic State, which has seized large swathes of Syria and Iraq in recent months.
In October, Egypt announced a three-month state of emergency in the governorate and a curfew from 5pm to 7am.
Authorities began demolishing houses and clearing residents along the Egyptian border with Gaza, to set a buffer zone in order to better fight the militant insurgency following a deadly attack by militants that killed 30 soldiers on 24 October.