The army in Mali says eight of its soldiers have been killed and five are missing after an attack by rebels in the north-eastern Archam region.
The fighting comes days after France and its allies said they were withdrawing their forces from Mali.
An army statement said that in response to this latest attack, the Malian air force killed 57 militants.
It said the soldiers were searching for rebel hideouts when they came under fire from "unidentified armed men".
There has been regional and international concern for Mali's security following the expulsion of French troops, as well as the foothold gained by Russian mercenaries in the region.
This week alone, locals told AFP new agency that 40 civilians had been killed in the same region of Archam where rival Islamist groups, including Islamic State, operate.
Mali has been grappling with jihadist unrest for years, prompting huge protests in 2020 against then-President Ibrahim Boubacar Keïta who was ousted by coup leaders promising to restore security.
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Since then country's new military leaders have had a series of disagreements with former colonial power France, which saw them reneging on an agreement to hold democratic elections this year and expelling the French ambassador when he objected.
It culminated in Mali ordering France to withdraw all of its troops, after almost 10 years fighting the jihadist threat.
Bolstered by soldiers from other Western nations, the Mali joint mission – called the Takuba Task Force – will now move a short distance across the border to Niger, remaining relatively close their current base.
Niger's president said on Friday that the country's borders would likely be more vulnerable to jihadist militant activity following the withdrawal of French forces and their allies from Mali.
Earlier this week he and other West African leaders met with French President Emmanuel Macron ahead of the announcement of the withdrawal of forces from Mali, during which they agreed that the troops would relocate to countries in the region.
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