Thirteen Chadian soldiers and 65 Islamist insurgents have been killed in heavy fighting in a remote part of northern Mali, Chad's military says.
It says Friday's clashes occurred in the Ifoghas mountains, where many militants are believed to be hiding.
Last month France led an operation to help oust Islamists who seized the vast northern region of Mali in 2012.
The US military says it has deployed surveillance drones in Niger to gather information on the Islamist militants.
The intelligence collected by a 100-strong contingent of US personnel from across the border is being shared with French troops in Mali, who are assisting thousands of troops from African states.
Islamist rebels are believed to have retreated to the Ifoghas mountains - a desert area in the Kidal region near the border with Algeria - after being forced from northern population centres in recent weeks.
In a statement issued late on Friday, the Chadian army said it had "destroyed five vehicles and killed 65 jihadists", adding that 13 of its soldiers had been killed and another five wounded.
Earlier this month, some 1,800 Chadian soldiers began patrolling the city of Kidal.
Chad has pledged to send 2,000 troops to Mali as part of the African-led mission.
Fighting between Islamist insurgents and Malian troops - backed by French soldiers - also continued in the central city of Gao.
On Thursday, the coalition said it had recaptured the city hall, which had been seized by militants a day earlier.
France intervened in January in its former colony, fearing that al-Qaeda-linked militants who had controlled Mali's north since April 2012 were about to advance on the capital Bamako.
The French have said they are planning to start withdrawing their 4,000 soldiers next month, and would like the African-led contingent to become a UN peacekeeping operation.