Answer:
Mali, Burkina Faso and Niger
Explanation:
They seized mining sites since 2016 in areas where the state is weak or absent.
Source: https://www.crisisgroup.org/africa/sahel/burkina-faso/282-reprendre-en-main-la-ruee-vers-lor-au-sahel-central#:~:text=In%20the%20central%20Sahelian%20countries,stretching%20from%20Sudan%20to%20Mauritania.