East Libyan forces said on Saturday that they had lost an Mi-35 combat helicopter near the central town of Zalla and that two crew members had been killed.
A military official for the eastern-based forces said it was not clear if the helicopter had been shot down or crashed because of a technical fault.
The forces lost contact with the helicopter on Friday.
Forces loyal to Khalifa Haftar, head of the Libyan National Army (LNA), have clashed repeatedly in the central desert region in recent weeks with rival brigades.
The LNA has been extending its control towards the west over the past few months, after largely defeating Islamist-dominated opponents in the eastern city of Benghazi.