MALIAN troops were poised on Saturday to reclaim a key town from Islamists threatening to advance on the capital after France sent in its air force, opening a dramatic new phase in the months-old conflict.
Witnesses and the Malian army said dozens of Islamist fighters were killed in the battle for Konna, one of the worst clashes since the start of the crisis almost a year ago and the most significant setback inflicted on the Islamists.
US officials said Washington might support France's sudden military involvement to help Bamako wrest northern Mali back from al Qaeda-linked groups, while Nigeria also said it had dispatched personnel on the ground.
Defence Minister Jean-Yves Le Drian said Operation Serval had already claimed its first French casualty when a pilot carrying raids to support Malian ground troops fighting for Konna was killed on Friday.
France also said it had deployed troops in Bamako, which has remained under government control since Islamist groups seized half of the country in March to protect its 6000-strong expatriate community.
A senior Malian officer in the region told AFP that the army was now fully in control of the town, after spending the best part of Saturday flushing out the last pockets of resistance.
"We control the town, all of it," said Lieutenant Ousmane Fane, a member of the Mopti regional command.
"We have claimed dozens of casualties, even around 100 among Islamist ranks in Konna."
Witnesses reached by AFP spoke of dozens of bodies strewn across the area, with one resident counting 46 dead Islamists.
The town, which had fallen into insurgents' hands on Thursday, is some 700km from Bamako but was seen as one of the last ramparts against an Islamist advance.
Mali's armed forces had been in disarray since a March coup and seemed powerless against a rebellion of seasoned mainly Tuareg fighters, but France's shock intervention tipped the power balance.
"The helicopters struck the insurgents' vehicles, which dispersed. The army is mopping up the city," a Malian military source said.
"During this intense combat, one of our pilots ... was fatally wounded," Le Drian told a press conference in Paris.
Groups with ties to al Qaeda in the Islamic Maghreb (AQIM) overpowered a secular Tuareg rebellion in March 2012 and seized control of a territory the size of France.
They have since destroyed centuries-old mausoleums which they see as a heresy in the fabled city of Timbuktu and imposed an extreme form of Islamic law -- or sharia -- in the main towns, flogging, amputating and sometimes executing transgressors.
The collapse of a nation seen as a democratic success story in the region sparked Western fears that northern Mali could become a major launchpad for global terrorist attacks.
The United States, former colonial power France -- which has eight hostages in the Sahel -- and the rest of the European Union had looked set to let the regional bloc ECOWAS take the lead on any military intervention, which appeared at least several months away.
The UN Security Council had okayed the regional mission but Mali's interim administration had warned it could not afford to wait months for a game-changer.
"Our choice is peace ... but they have forced war on us. We will carry out a crushing and massive retaliation against our enemies," Mali's interim leader, Dioncounda Traore, said in an address to the nation on Friday.
On Saturday he thanked France for its intervention.
French army chief Edouard Guillaud, speaking at the same briefing as the defence minister, said the operation had a tactical command in Mali.
French President Francois Hollande, who has struggled on the domestic front and seen his popularity hit record lows, said French forces would remain involved as long as necessary.
Nigeria's presidency on Saturday confirmed it had sent an air force technical team and the commander of the planned ECOWAS force to Mali.
