A government spokesman said the bodies were found near the city of Al Bayda, close to the site of the kidnapping.
The crew was taken in August while travelling through territory largely controlled by extremist militants.
Libya has been in turmoil since the fall of Muammar Gaddafi in 2011 and now has two competing governments and numerous militia groups.
Faraj al-Barassi, a district army commander in eastern Libya, told Reuters that militants loyal to Islamic State (IS) were responsible for the killings.
IS-affiliated militants have established a strong presence in parts of Libya, including Derna where the kidnapping is believed to have taken place.
Parts of Libya have descended into lawless chaos following the overthrow of Gaddafi, allowing extremists to gain ground.
A February report by Human Rights Watch said there was a "climate of impunity" in the country that "allowed militias to assault, threaten, kidnap, or even kill journalists".
Libya's internationally recognised government has fled from the capital Tripoli to the eastern city of Tobruk, while a rival parliament has been established in Tripoli itself.
Five journalists belonging to a Libyan TV crew have been found dead, eight months after they were kidnapped.