The commander of French anti-jihadist force Barkhane, General Laurent Michon, on Thursday accused "mercenaries" from Russian group Wagner of "preying" on Mali.
French-Malian relations started to nosedive after a military coup ousted Mali's elected president in August 2020.
The junta snubbed French appeals for an early return to civilian rule and then turned to Russian military operatives - "mercenaries" from the pro-Kremlin Wagner group, in France's view - to help its anti-jihadist fight.
Michon spoke as French forces finalise a withdrawal from Mali, bringing out military equipment via neighbouring Niger.
"The mining code in Mali has changed and now... a certain number of measures have been taken to exploit three gold sites for Wagner," he alleged.
"It's called preying, plain and simple."
The French general accused the group of acting like a drug "dealer", "giving Mali a first dose for free: protection against the nasty French" and quick fixes, before looking out for its own interests.
"In central Mali, they took 200 people prisoner, who were all executed soon afterwards," he said, criticising one such "rapid result by mercenaries".
But Michon said France's withdrawal from the Sahel country had nothing to do with "Wagner's arrival in Mali".
It was rather due to Bamako expressing its wish to "see us leave without delay", he said.
After leaving Mali, Barkhane would offer help only to countries requesting it - "on-demand support, adapted with flexibility to suit the intentions of such or such country".
Once France's pullout from Mali is done, only 2,500 French troops are to remain in the Sahel region.
Instead of acting in the place of local forces, French soldiers are to take on more of a supporting role, and the host country will take the lead, they say.
A 2019 report by the International Crisis Group estimated that up to 700,000 people worked in small-scale gold mining in Mali, producing 20 to 50 tonnes of the precious metal per year.