At least four eyewitnesses told ANSA they saw a young Muslim named Ahmad Hamed "burnt alive" by ISIS militants "in Rafah", a town in northeastern Sinai.
The eyewitnesses also said "his eyes were gouged out".
They said the man was killed under the accusation of collaborating with Egyptian authorities in the fight against ISIS in the area bordering the Gaza Strip.
Other Egyptians who worked with authorities to fight ISIS in the area have been killed in retaliation and as an attempt to deter others from collaborating.
There have been several cases of killings by throat slashing or decapitation - about 20 between 2013 and 2014, according to figures from an Egyptian site.
In northeastern Sinai, the Egyptian branch of ISIS (formerly known as Ansar Bait al-Maqdis) has been waging a bloody war for three years against the Egyptian army.
The military spokesman on his Facebook page announced that six "takfiri" (a term used to indicate ISIS militants) had been killed and 18 "suspects" were arrested.
The spokesman, who also said that two "weapons depositories" were destroyed, didn't specify the length of time in which the killings took place; however, they can be defined as frequent, with about 500 between September and the start of last month according to official sources.
Sources in Sinai said there had been "one dead among the recruits and three other wounded".