Javelin missiles found in a captured Libyan National Army base last month were bought by the French government from the United States, Paris said on Wednesday.
The French military said the projectiles were unusable and never meant for sale or transfer to any party in the Libyan conflict.
The missiles were intended for the “self-protection of a French military unit deployed to carry out counterterrorism operations,” the Army Ministry said in a statement.
“Damaged and unusable, the armaments were being temporarily stocked at a depot ahead of their destruction,” the ministry said.
The New York Times reported that the cache of four Javelin anti-tank missiles were found by militias fighting with the Libyan government in Tripoli against the Libyan National Army, which launched an offensive to capture the capital in April.
The militias reportedly found the Javelin missiles in a camp near Gharyan, in the mountains 80 kilometres south of Tripoli, after they recaptured the former key supply route for the LNA.
In April, Field Marshal Khalifa Haftar launched an offensive on Tripoli, vowing to cleanse the capital of the powerful militias that prop up the UN-backed government. The LNA already controls much of Libya’s east and south.
Field Marshal Haftar, who in recent years has battled extremists and other militias across eastern Libya, says he is determined to restore stability to the country.
He is increasingly seen by his allies, which include Russia and Egypt, as a bulwark against extremists in Libya who gained a foothold after the 2011 uprising that ousted Muammar Qaddafi.
The UN-recognised government in Tripoli headed by Fayez Al Sarraj controls a much smaller amount of territory in the east and draws support from Turkey, Qatar and Italy, analysts say.
In May, it posted pictures showing the arrival of Turkish BMC Kirpi armoured vehicles at Tripoli port.
France's role in the conflict under President Emmanuel Macron has caused tensions.
Mr Macron threw himself into diplomatic efforts to resolve the conflict after his elections in May 2017, seeing the instability across the Mediterranean as a major security worry and a source of migration to Europe.
French special forces and members of its DGSE intelligence service are known to be operating in Libya, which descended into chaos after a 2011 uprising and Nato-backed military campaign
France has publicly called for a UN arms embargo to be enforced, while an EU naval mission off the Libyan coast called Operation Sophia is trying to stop the flow of foreign weapons into the conflict.