"The authorities in Bamako announce 200 terrorists killed, without civilian casualties. I have a hard time believing, I have a hard time understanding, I have a hard time accepting these explanations," he said.

"There needs to be a United Nations investigation and we demand this," he added.

"It is the role of the United Nations to carry out this investigation... except that at the moment they do not have the ability to access the area of the centre where these atrocities were committed," he said.

Russia meanwhile has congratulated Mali on an "important victory" against "terrorism" and described as "disinformation" allegations about the massacre of civilians by Malian forces, as well as claims about the involvement of Russian mercenaries in the operation.

The Russian foreign ministry also accused the West of "staging" a campaign aimed at "putting the emphasis on Moscow's participation in war crimes".

Bamako denies the presence of mercenaries from the Russian group Wagner in Mali, acknowledging only the presence of Russian "instructors" and "trainers" under a bilateral cooperation agreement with Moscow dating from the 1960s.

In a report, Human Rights Watch said Malian soldiers and foreign fighters executed 300 civilians between March 27 and 31 in Moura.

The UN special envoy for Mali, El-Ghassim Wane, on Thursday called on the Malian authorities to provide access to the area.