Malian authorities have found a mass grave containing the bodies of soldiers in the southern garrison town of Kati, military and judicial sources said on Wednesday.

"They discovered the grave. It was known about for a long time, but there were more bodies than previously thought," said a senior military source.

A judicial source said the site, a short drive north of the capital Bamako, contained 21 bodies.

The discovery comes days after the detention of former junta chief General Amadou Sanogo, who led the March 2012 coup that plunged the West African country into chaos, for complicity in kidnapping.

A judicial source said at the time of Sanogo's detention that he had also been questioned over a failed counter-coup shortly after he seized power which caused more tensions between warring factions of the army.

It was not immediately clear if the soldiers in the mass grave had met their fate at that time.

Mali's newly elected President Ibrahim Boubacar Keita is battling to assert state control over the army, accused by human rights groups of excessive violence, torture and enforced disappearances.

Another challenge he faces is restoring state authority in the lawless north, which was occupied by separatists and Islamist militants until a French-led intervention in January scattered them.