The French air force carried out an air strike in Mali on Friday in support of government forces trying to push back Islamist rebels, French foreign minister Laurent Fabius said.
The French military intervention in the west African state is aimed at helping the Malian government resist a push south by rebel forces. Western powers fear the alliance of al Qaeda-linked militants that seized the northern two-thirds of Mali in April will seek to use the vast desert zone as a launchpad for international attacks.
"French forces brought their support on Friday afternoon to Malian army units to fight against terrorist elements," French president Francois Hollande told reporters. "This operation will last as long as is necessary." Hollande said United Nations security council resolutions meant France was acting in accordance with international laws.
Earlier, Hollande had made it clear that France would intervene to stop any further drive southward by Islamist rebels as Malian soldiers launched a counter-offensive to wrest back a town captured by militants this week. Mali's government appealed for urgent military aid from France on Thursday after Islamist fighters encroached further south, seizing the town of Konna in the centre of the country.
The rebel advance caused panic among residents in the nearby towns of Mopti and Sevare, home to a military base and airport. "We are faced with blatant aggression that is threatening Mali's very existence. France cannot accept this," Hollande said in a New Year speech to diplomats and journalists.
"We will be ready to stop the terrorists' offensive if it continues." The UN security council in December authorised the deployment of an African-led force supported by European states. "The French believe that France, and Europe, face a real security threat from what is happening in the Sahel," said Jakkie Cilliers, executive director of the Institute for Security Studies in South Africa.
A coup last March paved the way for a Islamist rebellion in Mali, which is Africa's third largest gold producer and a major cotton grower, and home to the fabled northern desert city of Timbuktu - an ancient trading hub and UNESCO World Heritage site that hosted annual music festivals before the rebellion.
Residents had seen Western soldiers arriving late on Thursday at an airport at Sevare, 60 km south of Konna. Sevare residents also reported the arrival of military helicopters and army reinforcements, which took part in the counter-attack to retake Konna overnight on Thursday in a bid to roll back the militant's southward drive.
"Helicopters have bombarded rebel positions. The operation will continue," a senior military source in Bamako said. A source at Sevare airport also said around a dozen war planes had arrived on Friday. A spokesman for the Nigerian air force said planes had been deployed to Mali for a reconnaissance mission, not for combat.
A spokesman one of the main groups in the Islamist rebel alliance said they remained in control of Konna. Asked whether the rebels intended to press ahead to capture Sevare and Mopti, the Ansar Dine spokesman, Sanda Ould Boumama, said: "We will make that clear in the coming days." He said any intervention by France would be evidence of an anti-Islam bias.
(Additional reporting by Richard Valdmanis in Dakar, Pascal Fletcher in Johannesburg, Alexandria Sage, John Irish and Elizabeth Pineau in Paris; writing by Daniel Flynn)