Around 20 people were killed in northern Mali when the vehicles they were travelling in came under attack earlier this week with local sources saying Wagner mercenaries and Mali's army were responsible.
Mali's military said there had been a "series of clashes" with "armed terrorist groups" in the area.
A relative of the driver of one of the vehicles from the northern city of Gao told French news agency AFP that the group was bound for Algeria when the deadly attack occurred.
"The driver of the first vehicle is my cousin," they said on the condition of anonymity.
"They encountered a group of Wagner mercenaries and some Malian soldiers who shot at them. In the first car, everyone died. My cousin too," they said, specifying that the passengers included migrants and nomads.
Mali's army said in a statement late on Monday that "seven terrorists" had been "neutralised" and weapons and ammunition recovered.
"Air strikes targeted a group of terrorists in the area of clashes, destroying a pick-up truck and neutralising its occupants," the army said, without commenting on the information from local sources.
A military source had earlier denied the claims, saying an investigation had begun but "the army killed no one".
"What happened is serious. These were civilians who were killed in the two vehicles in the Tilemsi region," a representative from the Gao region told AFP.
"In total, in the two vehicles, there are at least 20 dead," he said.
The separatist rebel group Front for the Liberation of Azawad (FLA) condemned the continuation of "ethnic cleansing carried out by the Bamako junta against the Azawad population".
The FLA statement claimed two vehicles "were intercepted by the terrorist coalition FAMA (Malian Armed Forces) / Wagner".
"Among the passengers, at least 24 people, including women and children, were coldly executed by the Malian army and Wagner's Russian mercenaries," the statement continued.
Mali, run by a military junta following coups in 2020 and 2021, has spent the past dozen years mired in a security crisis due to violence by groups affiliated to Al-Qaeda and Islamic State.
The military junta has been supported by Wagner mercenaries since breaking ties with former colonial ruler France.
The NGO Human Rights Watch in December denounced the "atrocities" committed against civilians by the Malian army and its Russian ally Wagner, as well as by Islamist armed groups.