"Abu Younis Jilabi Mansour, who is a senior member of al-Qaeda in the Islamic Maghreb was killed in artillery shelling by forces loyal to Libya's former army chief Khalifa Haftar near the city of Benghazi," the source, who requested anonymity, told The Anadolu Agency.
Al-Qaeda in the Islamic Maghreb (AQIM) is a branch of al-Qaeda militant group operating in North Africa.
Five others were killed along with Abu Younis, of which two were Algerian nationals, the source said.
"Abu Younis was likely killed on December 2 while present in an area that was under artillery shelling by Haftar forces. His body was found near the city of Benghazi," the source added. "He was identified through documents he had on him," he added.
"We're unsure as to why Abu Younis was in Libya; we don't think he was fighting Libyan forces, he might have on a weapons trafficking mission."
Abu Younis is wanted by Algerian security for joining armed militant groups in the 90s, after which he became a member of AQIM's top council.
Libya has been dogged by political instability since the 2011 ouster and death of long-ruling strongman Muammar Gaddafi.
In the more than three years since, rival militias have frequently locked horns, often bringing violence to the country's main cities, including capital Tripoli.