Civilians, they say, were encircled by government forces who refused to allow the opening up of an aid corridor to reach them.
A French military spokesman says weapons including assault rifles, machine guns and rocket launchers were air-dropped earlier this month.
A report in today's Le Figaro newspaper suggests that Milan anti-tank missiles may also have been included.
Arming the rebels is of course controversial, not least because in February, UN Security Council resolution 1970 established an arms embargo that appeared to apply to all sides in Libya. It talked about banning sales to the Libyan nation - the Libyan Arab Jamahiriya.
However there were those, not least the US Secretary of State Hilary Clinton, who argued that the subsequent UN resolution 1973 - the one that allowed all necessary means to be used to protect Libyan civilians - actually amended or overrode the earlier UN decision.
Legal differencesSpeaking in London in late March, she said that "there could be a legitimate transfer of arms if a country should choose to do that".
Continue reading the main storyDespite its efforts to frame its own arms supplies in terms of protecting civilians, it looks as though the French government has made a strategic decision ”End Quote But the US ambassador to the UN, Susan Rice, subsequently made it clear that Washington had not yet made such a decision.
British Prime Minister David Cameron took a similar position, noting that "the arms embargo applies to the whole territory of Libya, but at the same time UN Security Council resolution 1973 allows all necessary measures to protect civilians and civilian-populated areas."
Mr Cameron told the British parliament: "Our view is that this would not necessarily rule out the provision of assistance to those protecting civilians in certain circumstances."
That is not the interpretation many international legal experts put on Security Council resolution 1973. Indeed, it actually calls on governments "to ensure strict implementation of the arms embargo" established by resolution 1970. As is often the case, different experts differ on the exact legal interpretation.
Britain has been supplying the rebels with non-lethal assistance - things like uniforms, rations and radios. There has been a small British military team in Bengazi alongside the rebel headquarters, advising on logistics and other organisational matters.
Capable fightersNonetheless, weapons have been reaching the Libyan rebels in the east of the country, funded by Qatar and other Gulf States.
The article in Le Figaro suggests that some of these have also been flown in, to improvised airstrips in the west.
Despite its efforts to frame its own arms supplies in terms of protecting civilians, it looks as though the French government, whose aircraft fired the first shots in the Western-led intervention over Libya, has made a strategic decision.
The war is dragging on. Unease in some Nato countries is growing. Libyan rebels in the east of the country do not have the military means to march on the capital, Tripoli.
But the largely Berber forces in the Nafusa Mountains in western Libya have proved capable fighters. They have been advancing significantly in recent days.
They are much closer to the Libyan capital and thus better able to bring direct pressure on the Gaddafi regime.