Egypt's military said on Thursday that the leader of the Islamic State group's affiliate has been killed in the Sinai Peninsula, along with several key aides and 45 other members of the extremist group.

Few details were immediately available and there was no word from the extremist group's branch in Egypt on what, if confirmed, would be a major setback for Sinai-based militants.

A posting on the Facebook page of the Egyptian military's chief spokesman, Brigadier General Mohammed Samir, said Abu Doaa al-Ansari was killed in an operation south of the coastal city of el-Arish. It said the operation was carried out by counterterrorism forces backed by warplanes and guided by "accurate intelligence".

The statement did not provide a total number of those killed or say when the operation took place, but two military officials with firsthand knowledge of the conflict in the turbulent northern part of Sinai said Ansari and his aides were killed in an airstrike that targeted a house located amid olive groves south of el-Arish.

Aerial images of the strike released by the military appeared to confirm the account given by the officials, who spoke on condition of anonymity because they were not authorized to discuss the operation with the media.

The name of Ansari is not widely known and had not been previously mentioned as that of the leader of the extremist group, which was known as Ansar Beit al-Maqdis, or Soldiers of Jerusalem, before it swore allegiance to the IS group fighting in Syria and Iraq.

Doubts remain

Ansari's name is likely a nom de guerre - something militants typically take when joining groups such as the IS. These names often allude to the country or city a militant hails from or the place he adopted as his home.

Mohannad Sabry, an Egyptian expert on Sinai insurgency, said it was a "seriously embarrassing situation" that the military did not provide Ansari's real name, something he said casts doubts on the purported leader's identity and the report of his death.

"Even if someone with this nom de guerre exists, this will be one more time Egypt's military announces that it has killed the leader, or a leader of a group that never publicly named its leader," Sabry said.

According to the Egyptian military officials, the airstrike that killed Ansari was part of an ongoing, intense air campaign that began more than a week ago and in which jet-fighters, helicopter gunships and drones are being used. The campaign of airstrikes, at least in part, were in response to the growing threat to ground troops posed by roadside bombs planted by the militants, they said.