"The forces raided ten vast farms belonging to the extremists and managed to kill five of them and arrest two after a fierce confrontation," the source added.
The security forces seized a large ammunition warehouse, stocks of black military uniform of Islamic State (IS) regional terrorist group and other military camouflage outfit, a military training yard and video shooting units.
According to the source, the farms were the main den of Al-Qaida-inspired Ansar Bayt al-Maqdis (ABM) group that has recently pledged allegiance with the IS and changed its name to "Sinai State" as a group loyal to IS leader Abu Bakr al-Baghdadi.
"The militants who confronted the security forces presented a cover for leading ABM member Abu Osama Al-Masri until he ran away through the back yards," the source said, noting that dozens of extremists managed to escape during the raid.
Egypt has been facing a rising wave of terrorist attacks since the military ousted former Islamist President Mohamed Morsi in July 2013. The following crackdown on Morsi's supporters has left about 1,000 killed and thousands more injured and arrested. Anti-government attacks have since extended from the restive Sinai to Cairo and other provinces across the country.
The security forces have intensified anti-terror military operations and raised alert level in Sinai in the wake of a car-bomb attack that killed around 30 Egyptian soldiers in late October.
The ABM group, which was founded in 2011 and has claimed responsibility for dozens of deadly attacks against Egypt's military and police personnel, has been designated by Egypt and the United States as a terrorist organization.