The announcement comes just hours after the French army said it had filmed Russian mercenaries burying bodies near the base to falsely accuse France's departing forces of leaving behind mass graves.

The video, filmed with a drone and seen by AFP on Thursday, showed what appear to be Caucasian soldiers covering bodies with sand near the Gossi base.

"Bodies in a state of advanced putrefaction were discovered in a mass grave, not far from the camp formerly occupied by the French force Barkhane", the army's general staff said in a statement.

France officially handed control of the Gossi base to the Malian army on Tuesday as part of a withdrawal announced in February.

"The state of advanced putrefaction of the bodies indicates that this mass grave existed well before the handover. Consequently, the responsibility for this act can in no way be attributed to the Fama", or Malian armed forces, the statement said.

The defence ministry has been asked to open an investigation.

France and the United States have accused Russian Wagner mercenaries of deploying in Mali as Paris winds down its almost decade-long military operation in the Sahel country.

Mali's military-dominated government has denied the accusations and said the Russians in the country are military instructors.

Anti-French sentiment has grown in West Africa, where French forces have operated since 2013 to stem jihadist insurgencies, and social media campaigns have targeted French troops.

France's pull-out from Mali came as swathes of territory remained under the control of rebels linked to Al-Qaeda and the Islamic State group and as tensions spiked between Paris and Bamako over the alleged deployment of Wagner mercenaries.