Oil-rich Libya slid into chaos after veteran dictator Moamer Kadhafi was toppled and killed in a NATO-backed uprising three years ago.
Weapons looted from his arsenal have made their way to the so-called "Salvador Triangle", a no-man's land formed by the porous borders of Libya, Algeria and Niger, experts say.
For years the triangle was the backyard of smugglers and traffickers through which illicit weapons flowed easily between north Africa and countries in sub-Saharan Africa.
On October 10, France said its forces had destroyed a convoy belonging to Al-Qaeda's north African branch in Niger that was carrying arms from Libya to Mali.
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The operation was part of a counter-terrorism campaign led by France to flush out jihadists, including Al-Qaeda in the Islamic Maghreb (AQMI), from the Sahel region.
Jihadists had occupied the desert north of Mali for 10 months before they were ousted in January 2013 in a French-led military intervention.
"It is very difficult for any army to control such a vast region, unless it has sophisticated technology" because the jihadists "know very well the terrain and can set up camps despite harsh conditions."
An intelligence official, who declined to be named, told AFP that jihadists have set up three "secret camps" in southern Libya where hundreds of militants are training to fight in Mali, Iraq or Syria.
"These camps have become the key providers of combat-ready jihadists," the source said.
"Drones have spotted training camps and Western intelligence officers have been to these places," he said.
"I don't have precise figures. But I'm sure that there are Libyans among these jihadist groups," added Pack, a researcher on Libya at the University of Cambridge and president of Libya-analysis.Com.