A French soldier and "more than 20" Islamist insurgents were killed in heavy fighting in northern Mali Tuesday, President Francois Hollande and his Defence Ministry said, DPA reported.
The mission "was attacked by terrorist groups," triggering a firefight that lasted several hours and in which "more than 20" insurgents were killed, it continued.
French armoured vehicles and two Mirage fighter jets intervened to support the ground forces.
The clashes, which Hollande described the clashes as "serious", came a day after French and Malian forces launched an operation to try to rout the insurgents from the mountainous area to which they retreated after being pushed out of northern Malian towns.
The militants from three groups are believed to be holding seven French nationals hostages in the region.
A further seven French citizens - three adults and four children - were kidnapped on Tuesday in northern Cameroon, near the border with Nigeria. The French government said it suspected the Nigerian Islamist group Boko Haram of being behind that attack.
The kidnapping coincided with a ramping-up of troop levels in northern Mali.
The French Defence Ministry said African forces had been increased to 5,250 - some 3,000 West African troops and around 2,000 from the central African country of Chad. There are plans to deploy almost 3,000 more.
A Malian army spokesman said that the joint French and African forces were working on strengthening security around the former rebel strongholds of Gao and Timbuktu.
France launched its offensive on January 11 against the Islamist rebels who were advancing on the capital Bamako in the south.
The last known Islamist base of Bourem, about 1,300 kilometres north-east of Bamako, was liberated by French forces at the weekend.
While the military operation continues Mali's government is also being pressed to offer concessions to the people of northern Mali whose disillusionment with the central government the jihadists have sought to harness.
At a press conference in Paris Malian Prime Minister Diango Cissoko rejected charges that the government had neglected northern Mali while launching an appeal for increased development aid.