Volker Turk also expressed alarm at the killing of around 30 others in attacks at the weekend in central Mali, a particular hotbed of violence.
"I am appalled by credible allegations that Malian armed forces accompanied by foreign military personnel summarily executed at least 25 people in Welingara village, in the central Nara region on 26 January," Turk said in a statement.
"I am also alarmed by reports that about 30 civilians were killed in attacks by yet unidentified gunmen on two other villages — Ogota and Oimbe —in the Bandiagara region over this past weekend," he added.
Gathering and verifying information in Mali is made difficult by the country's vast geography, deteriorating communications and security concerns.
Jihadist violence that started in northern Mali in 2012 spread to the center of the country in 2015, when Katiba Macina — an al-Qaida-affiliated group — was established, led by the Fulani preacher Amadou Kouffa.
Mali is led by a junta that seized power in 2020 and turned away from former colonial power France, before pushing the UN stabilization mission MINUSMA to leave at the end of 2023.
The junta has chosen instead to pivot towards Russia, both politically and militarily.
Many observers claim it has enlisted the services of Russian mercenaries, despite constant denials.
The UN and local sources regularly accuse the Malian army and its allies of abuses against civilians, which they systematically deny.
UN rights investigators say Malian troops and foreign forces — presumed to be Wagner — were behind the massacre of at least 500 people in the central Malian town of Moura in March 2022.
"It is essential that all allegations of arbitrary deprivations of life, including summary executions, are fully and impartially investigated and those found responsible brought to justice in trials observing international standards," the UN rights chief said Thursday.
To date, none of the investigations launched in Mali into abuses by the military have been successful.
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