The al-Qaeda-linked rebels overran the garrison village of Diabaly in central Mali, France's defence minister said in Paris on Monday.
Jean-Yves Le Drian said the rebels "took Diabaly after fierce fighting and resistance from the Malian army that couldn't hold them back"'.
The Malian military is in disarray and has let many towns fall with barely a shot fired since the insurgency began almost a year ago in the northwest African nation.
French military forces, who began battling in Mali on Friday, widened their aerial bombing campaign against the rebels occupying northern Mali, launching airstrikes for the first time in central Mali to combat the new threat.
Al Jazeera's correspondent Nazanine Moshiri, reporting from the capital Bamako, said: "There are reports of about 60 fighters being killed thus far while Doctors without Borders say they are very concerned about the lives of civilians in the region."
The rebels, who come from several nations besides Mali, had been bottled up in the narrow neck of central Mali. But by now sweeping in from the west, they are now only 400km from Bamako, in southern Mali.
Before France sent its forces in on Friday, the closest known spot the rebels were to the capital was 680km away, although they might have infiltrated closer than that.
'Africanisation' of conflict
France is urging the "Africanisation" of the conflict, encouraging African nations to send troops to fight the rebels.
There have been promises, but no troops movements have yet been publicly announced.
Early Monday, an intelligence agent confirmed that shots rang out near the Diabaly military camp in what was still nominally government-held territory and that soon after, jets were heard overhead, followed by explosions.
The agent insisted on anonymity because he is not authorised to speak publicly on the matter.
A Malian commander in the nearby town of Niono said the bombardments did not stop the fighters and that they occupied Alatona.
The commander said that on Monday, the rebels succeeded in reaching the north-south road which connects Diabaly to Segou, the administrative capital of central Mali.
Safety of civilians
The international medical humanitarian organisation Doctors Without Borders (MSF), said on Monday that 12 people wounded in the conflict were being treated by an MSF team at a regional hospital in Timbuktu, a roughly seven-hour journey from the conflict zone.
"We are worried about the people living close to the combat zones, and we call on all the parties to the conflict to respect the safety of civilians and to leave medical facilities untouched,'' Rosa Crestani, MSF emergency response coordinator, said.
Mali's north, an area the size of France itself, was occupied by al-Qaeda-linked rebels nine months ago, following a coup in the capital.
In December, the United Nations Security Council adopted a resolution calling for a military intervention, but only after an exhaustive list of pre-emptive measures were fulfilled, starting with training the Malian military, which was supposed to take the lead in the offencive.
All of which changed in a matter of hours last week, when French intelligence services spotted two rebel convoys heading south, one on the mostly east-west axis of Douentza to the garrison towns of Mopti and Sevare, and a second heading from a locality north of Diabaly toward Segou, the administrative capital of Central Mali.
Had either Segou or Mopti fallen, many feared that the rebels could advance toward the capital. That concern was the main factor that prompted the swift intervention.