The "accumulated shortfall for the state" from overbilling and non-delivery of military gear totalled more than 32.6 billion CFA francs (49.7 million euros/$55.1 million), state prosecutor Maman Sayabou Issa said, citing a "final audit" by the defence ministry.

The affair sparked an outcry when excerpts of a preliminary audit began appearing on social media, showing misappropriations totalling more than 76 billion CFA francs or 116 million euros between 2017 and 2019.

"The preliminary report contained contradictions that were incorporated in a definitive report dated April 3, 2020," the prosecutor's statement said.

The findings point to possible criminal activity, the statement said, citing evidence of fraud, use of false documents, "illicit enrichment" and procurement irregularities.

The scandal dates to late February when the government announced that an audit requested by President Mahammadou Issoufou revealed overbilling and non-delivery of orders to the army, which has been fighting a jihadist insurgency in the southeast and west of the country since 2015.

On March 15, protests descended into violence between demonstrators and security forces. At least three civil society figures remain in custody.

Niger ranks as the poorest country in the world, placed at 189th out of 189 nations in the UN's Human Development Index.