N'DJAMENA Chadian troops attacked an Islamist base in northern Mali on Saturday in heavy fighting which France called part of the final campaign to drive al Qaeda from its mountain hideouts.
Thirteen Chadian soldiers and 65 al Qaeda-linked rebels were killed on Friday in the Adrar des Ifoghas mountains near the Algerian border, where French special forces are also hunting Islamist bases, Chadian military sources said.
A senior Chadian military source said on Saturday his country's heaviest losses during the international offensive in Mali centred around a rebel base that appeared to be of "significant importance" as the militants were not fleeing.
The violence underscores the risk French and African forces become entangled in guerrilla war as they help Mali's weak army.
French troops were also fighting in the Adrar area, French President Francois Hollande told a news conference, in what he called a "last phase" of the campaign begun when Paris sent troops to Mali last month to stop a southward push by Islamist rebels who seized control of the north last April.
"These battles will continue," Hollande said on Saturday. "It is the last phase because it is most likely that AQIM's (al-Qaeda's north African arm)forces are hiding there."
Troops from neighbouring African nations - including 2,000 Chadians - have deployed to Mali and are meant to take over leadership of the operation when France begins to withdraw forces from its former West African colony next month.
Five people, including two Islamists, were also killed in In Khalil - a town bordering Algeria 1,700 km (1,000 miles) northeast of the capital Bamako - on Friday in car bomb attacks on Tuareg MNLA rebels with French links, an MNLA spokesman said.
The pro-autonomy MNLA rebels are helping the French to fight al Qaeda and its allies. It was the MNLA's defeat of Mali's army last year that triggered a coup in Bamako and sparked chaos allowing the Islamists to launch their own campaign.
The Tuareg fighters' Paris-based spokesman Moussa Ag Assarid said on Saturday the MNLA came under heavy machine gun fire from "terrorist" groups in In Khalil, most likely Islamists.
France 24 television reported local Arab groups said they had launched attacks against the Tuareg MLNA rebels.
It is hard for Reuters to verify such reports from Mali's extreme north because of restrictions on media travelling there.
After driving insurgents from northern towns such as Gao and Timbuktu, France and African allies have focused on the remote northeast mountains and desert - an area the size of France - that includes networks of caves, passes and porous borders.
They believe some of eight French hostages held by al Qaeda-linked groups are being kept in the area.
U.S. President Barack Obama said on Friday he deployed about 100 troops to neighbouring Niger for unmanned reconnaissance flights over Mali to share intelligence with French forces.
Paris has said it plans to start withdrawing some of its 4,000 troops from Mali next month. But rebels have fought back against Mali's weak and divided army, and African forces due to take over the French role are not yet in place.
A Malian military source said on Saturday they had recovered 23 Islamist bodies from Gao, where French and Malian troops fought Islamists on the streets earlier in the week.