With strong backing from France, a UN envoy has demanded access to the Malian village of Moura, the site of an alleged massacre last month by local forces and suspected Russian fighters.
The UN's peacekeeping mission in Mali, MINUSMA, was able to fly over the site on 3 April.
But its envoy for the Sahel nation, El-Ghassim Wane, told the Security Council on Thursday that an "integrated mission" had yet to receive then green light "despite extensive engagement with the national authorities".
On Thursday, Mali said military investigators were looking to events in Moura after rights groups said about 300 people were executed during an operation last month against militant Islamists.
Wane said he welcomed the investigation. MINUSMA also welcomed the development in a separate statement.
However, he added, "it is imperative that the Malian authorities extend the necessary cooperation for MINUSMA to have access to the site of the alleged violations, in line with its mandate".
France, whose relations with Mali's transitional government have soured of late, has strongly supported Wane's demand.
"It would allow the perpetrators of these acts, some of which could amount to war crimes, to be brought to justice," said France's UN ambassador, Nicolas de Rivière.
"France has noted the opening of an enquiry by the prosecutor in Mopti. It is essential that MINUSMA be able to carry out its own enquiry – unimpeded and fully independent," Rivière added.
Wagner mercenaries
Mali's army announced on 1 April that it had killed 203 militants in Moura, in central Mali, during an operation in late March.
However, that announcement followed widely shared social media reports of a civilian massacre in the area.
Human Rights Watch (HRW) said this week that Malian forces and foreign fighters killed 300 civilians in Moura in late March, in what it called "the worst single atrocity reported in Mali's decade-long armed conflict."
Several witnesses and other sources identified the foreign soldiers as Russians to HRW.
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Russia has supplied what are officially described as military instructors to Mali, which has been battling a brutal jihadist conflict since 2012.
The United States, France and others say the instructors are operatives from the Russian private security firm Wagner.
Wane told the Security Council that MINUSMA has opened 17 investigations into allegations of indiscriminate attacks on civilians, extrajudicial arrests and killings, mistreatment and forced disappearances in central Mali since the beginning of this year.
Pointing to the rise in reported rights abuses, Richard Mills, the US deputy ambassador to the UN, told the council it was "exactly why the United States continues to warn countries against partnering with the Kremlin-linked Wagner Group".
(with newswires)