Government forces in Mali say they have regained territory from Islamist militants following air strikes by the French military.
Malian officials said they had taken back the strategic central town of Konna, which rebels had secured just a day earlier as they pushed south.
The news came hours after France announced it had begun military operations in support of Mali's army.
Armed groups, some linked to al-Qaeda, took control of northern Mali in April.
The BBC reports the Islamists have sought to enforce an extreme interpretation of Islamic law in the area.
Regional and western governments have expressed growing concern about the security threat from extremists and organised crime.
Announcing France's military intervention, French President Francois Hollande said Islamists had been trying to turn Mali into a "terrorist" state.
He said the intervention complied with international law, and had been agreed with Malian interim President Dioncounda Traore.
Residents in Mopti, just south of Konna, said they had seen French troops helping Malian forces prepare for a counter-offensive against the Islamists.
Mr Traore declared a state of emergency across Mali, which he said would remain in place for an initial period of 10 days.
Late on Friday Malian officials said they gained control of Konna.
"Konna is under our control this evening but we are still conducting mopping-up operations," said Lt Col Diarra Kone, though he warned that some rebels might still be in the town.
France ruled Mali as a colony until 1960.