The government of Mali says at least 25 soldiers have been killed and about 60 are missing in attacks by suspected jihadists on two military posts near the border with Burkina Faso.
As intense fighting continued, the government said it had also lost significant equipment following the Tuesday attack.
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In response Malian troops, with air support, have begun a joint operation with forces from Burkina Faso.
Jihadist violence and ethnic rivalries have caused conflict in Mali since 2012.
Mali is part of a five nation anti-insurgency force operating in the Sahel. It includes Burkina Faso, Chad, Niger and Mauritania.
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The G5 Sahel, as it is called, is backed by a 3,000-strong French force.
The UN Secretary General Antonio Guterres has expressed concern over escalating violence in the region, where civilian deaths increased four-fold between 2012 and 2018.
Source:Â bbc.com