French planes have bombed Islamist rebel camps in the far north of Mali, the day after French President Francois Hollande visited the West African country.

Thierry Burkhard, spokesman for the French army in Paris, said the overnight raids targeted logistics bases and training camps used by the al Qaeda-linked rebels near the town of Tessalit, close to the Algerian border.

"These were important air strikes," he said.

France claims the rebels are holding seven of its citizens hostage, seized in recent years in the Sahara.

Malian military sources said French and Chadian troops had clashed with members of the Ansar Dine militant group in the region around Kidal on Saturday.

French attack helicopters and transport planes carrying special forces left the city of Gao to reinforce the French and Chadian contingent stationed at the airport in Kidal.

France has deployed 3,500 ground troops, fighter jets and armoured vehicles in the three-week-old Operation Serval (Wildcat) which has broken the Islamists' ten-month grip on the towns of northern Mali, where they violently imposed sharia law.