Army says eight soldiers escaped attack on around a dozen vehicles in northwest Bouka Were, around 100 kilometres from border with Mauritania.
A weekend ambush on a military convoy in Mali left 24 soldiers dead and an unspecified number missing, the army said on Monday, blaming the assault on militants.
In posts on social media, the army did not enumerate the missing but said eight soldiers escaped the attack on around a dozen vehicles on Sunday at Bouka Were, around 100 kilometres from the border with Mauritania.
It was the latest in a string of assaults by militants who unleashed a revolt in northern Mali in 2012 that has spread to Burkina Faso and Niger despite the presence of thousands of French and UN troops.
The attack is the deadliest since a November 2019 attack when 54 soldiers were killed during an assault on an army post in the north of the country.
A senior military official said earlier that some of the vehicles were able to extricate themselves from the ambush, but that of the 64 troops who had been in the convoy, only about 20 were present at a roll call, the source said.
"A search is under way to determine the fate of soldiers who have been listed missing," he said on condition of anonymity.
Another military officer and an official in the nearby town of Diabaly, who also asked not to be named, confirmed his account.
The militant insurgency, mainly led by groups linked to Al-Qaeda or Daesh, has claimed thousands of military and civilian lives and forced hundreds of thousands from their homes.
Violence in recent months has engulfed central Mali, an ethnic mosaic where the state exercises little control and militants atrocities feed tit-for-tat assaults among rival communities.
The al-Qaeda-linked group Katiba Macina, led by an ethnic Fulani (Peul) called Amadou Koufa, is recruiting among the Fulani herding community, which has long been at odds with the Bambara and Dogon farming groups.
These groups, in turn, have created their own "self-defence" organisations.
On Saturday, two Egyptian soldiers with the UN peacekeeping force MINUSMA were killed when their convoy came under attack in northwestern Mali, the United Nations said.
President Keita under pressure
The violence has weakened the hand of President Ibrahim Boubacar Keita, who is facing a rising clamour of protest and demands for political renewal.
Tens of thousands of people rallied in the capital Bamako on June 5 on the heels of demonstrations in May over the outcome of parliamentary elections, which the president won, as well as over coronavirus restrictions.
More protests have been scheduled for this Friday.
Keita, who has been in power since 2013 in the former French colony, on Sunday reached out to the coalition behind the protests, saying, "My door is open and my hand always extended."
Surge in militant attacks
After militant attacks surged in February, Keita broke with precedent to say that he was seeking to forge a dialogue with certain rebel leaders.
"The number of deaths in the Sahel is becoming exponential and it's time that certain paths be explored," he said in an interview with French media.
However, Keita said at the time of his announcement that he had not received a response from militant leaders, and indications have yet to emerge that any such dialogue has developed.