A former US ambassador to Mali has told the BBC that France paid ransom money to free hostages and the funds ended up bolstering Islamist groups it is now fighting.
Vicki Huddleston said France paid $17m (£10.75m) to free hostages seized from a uranium mine in Niger in 2010.
She said other European countries, including Germany, had also paid ransoms amounting to nearly $90m.
France has always denied that it pays ransoms for the release of hostages.
It is struggling to maintain order two weeks after French-led troops began an assault on Islamist militants who took over large parts of northern Mali.
On Friday, a suicide bomber blew himself up near a group of soldiers in the northern town of Gao, injuring one of them, in an attack claimed by an al-Qaeda offshoot.
Meanwhile, army infighting in the capital left one person dead and five injured when heavily-armed regular soldiers clashed with elite “Red Beret” paratroopers at their base in the capital Bamako.
Trainers arrive
Ms Huddleston said the hostages kidnapped at the Niger mine in 2010 were only released because money had changed hands.
“All the European countries who paid ransoms have denied that they paid ransoms and you know perhaps they can deny it because it’s gone indirectly through various channels in the Malian government,” she told the BBC’s Newshour programme.
BBC’s Thomas Fessy: “This is a city on the edge… the people here wonder what is to happen next”
“When I was in Mali I actually knew, he was the Governor of Gao, who’s now deceased, and he was one of the negotiators with the AQIM (Al-Qaeda in the Islamic Maghreb).”
Al-Qaeda branches, she added, are “not releasing the Western hostages out of the goodness of their hearts”.
Friday’s violence coincided with the arrival of 70 EU trainers – the first of 500 military instructors to be deployed to support the Malian army.
Colonel Bruno Heluin, commander of the group, said the aim was to “enable the Malian army to hold all the nation’s territory, and so that Mali can have a good army at its disposal, prepared to engage”.
Some 4,000 French troops have retaken control of the north’s main towns, and are now, along with some 1,000 Chadian troops, moving into the mountains near the Algerian border where the militants are reported to have fled.
They said on Friday they took Tessalit, a strategic town in the mountains with its own airport.