An Egyptian director at Libyan TV station Barqa, who was kidnapped in August 2014, was confirmed dead on Monday, his cousin, journalist Doaa Sultan, announced on her Facebook page.
Mohamed Galal Okasha, 31, was kidnapped in August 2014 along with four of his Libyan work colleagues.
A district army commander, Faraj Al-Barassi, told Reuters that all five dead bodies were found, with slit throats, outside the eastern city of Baydha near Derna, which is controlled by the Islamic State group in Libya.
Al-Barassi said all five men were killed by militants loyal to the Islamic State group in Libya.
Sultan said a member of the Islamic State group in Libya had told Bayda authorities that the militant group killed Okasha, his TV crew and 30 others, before leading officials to the place where all the dead were buried.
Sultan said that officials in Bayda, who were able to successfully identify the bodies of the murdered Libyan citizens, failed to send the right casket carrying Okasha body to Tunisia on its way back home. The casket Libyan authorities sent to Tunisia contained the corpse of a different deceased Egyptian, she said.
According to Sultan, Okasha's family had submitted an official request to the foreign ministry asking for assistance in the repatriation of his body.
Foreign ministry spokesperson Badr Abdel-Aty told Ahram Online that the ministry is discussing issues related to the Okasha case with the Egyptian ambassador in Libya, but declined to elaborate.
Following the ouster of long-time dictator Muammar Ghaddafi and a short-lived invasion of the country by NATO in 2011, various Libyan militias have been fighting the central government in a civil war that has ravaged the country.
An internationally-recognised parliament operates out of the city of Tobruk in the east, while anti-government rebels control the capital Tripoli in the west.
The Islamic State group in Libya is one of several Islamist militias fighting against Tobruk.
Bayda, where Okasha's body was found, lies in the east of the country and falls under the control of Tobruk.
In late 2014, the IS group in Libya decapitated 20 Coptic Egyptian migrant workers near Derna.
Hundreds of thousands of Egyptians have worked in the oil-rich north African country for decades.
However, since the start of the civil war, thousands of Egyptian labourers have fled Libya.
Many Egyptians have been kidnapped by militias across Libya, and remain missing in different parts of the country.