The late yesterday killing in the coastal city of al- Arish came one day after the Islamic State group's local affiliate warned it would escalate attacks against Christians.
The officials spoke on condition of anonymity because they were not authorised to speak to media.
Ayoub is at least the seventh Christian in northern Sinai to be killed by suspected IS militants in recent months. The killings have forced hundreds of Christians to flee the region.
At least 75 others have been killed in IS attacks targeting churches since December.