The Mauritanian Foreign ministry accused the Malian army of crimes against its nationals, on Tuesday.
The ministry summoned the Malian ambassador to protest the recurring acts.
The move came after Mauritanians civilians disappeared in unclear circumstances at the border region of Adel Bagrou.
Audio files allegedly recorded by eyewitnesses circulating on social media directly incriminated Mali’s army.
In January, seven Mauritanians died in the same region and after an inquiry, Bamako said there was no evidence linking its army to the deaths.
However, tensions didn't subside.
Dozens of people demonstrated in near the presidency in Nouakchott, demanding an end to the disappearances.
Since ECOWAS sanctions hit Mali, the transitional authorities had found in Mauritania a privileged partener.