Thirteen suspected militants were killed in a raid on Tuesday in the Egyptian Mediterranean coastal city of el-Arish' el-Obour neighborhood, officials announced.
They said police found weapons and explosives in the hideout, and forensic teams are now identifying the bodies.
The officials spoke on condition of anonymity as they weren't authorized to talk to reporters.
Egypt has battled an insurgency led by an ISIS affiliate for years in Sinai, which occasionally spills over to the mainland.
Separately, officials said a police conscript has been killed in a militant attack in the restive northern part of the Sinai Peninsula.
They said the attack, which took place late on Monday in the town Sheikh Zuweid, also wounded three other policemen who were taken to a nearby hospital for treatment.