Witnesses told Egyptian media it happened in the town of Bir al-Abed near al-Arish during Friday prayers.
Local police said men in four off-road vehicles opened fire on worshippers during Friday prayers, AP reported.
Egypt has been fighting an Islamist insurgency in the region, which has intensified since 2013.
The latest attack comes weeks after a deadly militant ambush of Egyptian soldiers in Sinai.
This is a developing story