Overnight, France launched airstrikes on the town of Kidal, 1,500 kilometres north of the Malian capital Bamako. A Malian security source said the home of Ansar Dine chief Iyad Ag Ghaly was destroyed in the air raids.
Kidal has been a bastion of Ansar Dine, whose leader is a former soldier and a Tuareg ex-rebel who formed the group last year.
It came a day after French and Malian troops seized the major town of Gao from another Al Qaeda-linked group, the Movement for Oneness and Jihad in West Africa, MUJAO.
Gao is the biggest of six towns seized by the French and Malian troops since they launched their offensive on January 11 to wrest the vast desert north from the Islamists, who imposed a particularly brutal version of sharia law in areas under their control.
The French offensive got a fresh boost with Washington deciding on Saturday to step up its role in the conflict by helping refuel French warplanes, a Pentagon spokesman said.
US Defence Secretary Leon Panetta and French counterpart Jean-Yves Le Drian also discussed plans for the Americans to transport troops from African nations, including Chad and Togo, to facilitate the international effort in Mali.
The US military has more than 400 tankers equipped to refuel fighters and other warplanes in mid-air. France has about 14 such tankers.
Meanwhile, outgoing African Union chairman Boni Yayi thanked France at a summit of the 54-member organisation in the Ethiopian capital Addis Ababa.
"I want to salute France," Benin's president told the summit, saying the AU response had been slow, and that France's action was something "we should have done a long time ago to defend a member country".
West African defence chiefs have agreed to boost their troop pledges for the force to 5,700 from the previous 4,500.
Chad, which neighbours Mali but is not a member of the Economic Community of West African States (ECOWAS) raising the force, has promised an additional 2,000 soldiers.
So far however, only a fraction of the African troops have arrived in Bamako.
France has already deployed 2,500 troops to Mali and its defence ministry says 1,900 African soldiers are on the ground there and in Niger.