"Three bodies were found after being killed by unidentified assailants," the source, requesting anonymity, told The Anadolu Agency.
He said that the attackers had dumped the three bodies on main roads.
"Two of the bodies were decapitated, while the third bore several gunshot wounds to the head," the source said.
There has been no claim of responsibility for the incident.
According to residents and security sources, nine people – including the three found Saturday – had been kidnapped by militants in the past two weeks.
It is believed that militant groups in Sinai kill those suspected of "cooperation" with Egyptian or Israeli authorities.