France has air-dropped weapons to rebels fighting Col Muammar Gaddafi's troops in Western Libya, the French military has confirmed.
Light arms and ammunition were sent to Berber tribal fighters in the Nafusa mountains in early June, it said.
Earlier, a report in Le Figaro newspaper said the arms included rocket launchers and anti-tank missiles.
France, a leading force in the Nato operation in Libya, did not inform its allies about the move, Le Figaro said.
"We began by dropping humanitarian aid: food, water and medical supplies," said Col Thierry Burkhard, spokesman for the French general staff.
"During the operation, the situation for the civilians on the ground worsened. We dropped arms and means of self-defence, mainly ammunition," he told AFP news agency.
He said the arms were "light infantry weapons of the rifle type", dropped over a period of several days "so that civilians would not be massacred".
The BBC's Christian Fraser in Paris says the statement is likely to bring further criticism from the likes of Russia and China, who believe Nato and its allies have already gone beyond the remit of UN resolution 1973, which authorised international military action in Libya.
The US has argued that resolution 1973 allows countries to provide arms to rebels despite an earlier resolution - 1970 - that imposed an arms embargo on the whole of Libya.
Resolution 1973 authorises "all necessary measures" to protect civilians, "notwithstanding" the arms embargo in resolution 1970.
France played a prominent role in pushing for military intervention in Libya, and French and British planes have led the air strikes over the country that began in late March.
Qatar, which has supported the Nato-led operation in Libya, has been supplying arms to rebels mainly through their eastern stronghold in the city of Benghazi.
France, the UK and Italy announced in April that they were sending military advisers to Benghazi.
The decision to drop arms to the Libyan rebels was reportedly taken following a meeting in mid-April between French President Nicolas Sarkozy and the Chief of Staff of the Libyan rebels, Gen Abdelfatah Younis.
France is said to have been concerned at the stalemate in a conflict between the rebels and pro-Gaddafi forces that started in February.
Local media reports say 40 tonnes of weapons were sent to western Libya, including "a few light tanks" that were smuggled in across the Tunisian border.
Le Figaro also reported that it had seen a confidential defence map showing two makeshift airstrips in rebel-held towns, built to receive small aircraft from the Gulf that can move arms closer to the front.
The rebels have recently been edging forward in Libya's north-west, and are hoping to push on to Tripoli from the frontline, currently on the other side of the Nafusa mountains and about 65km (40 miles) from the capital.