After taking power in a coup in 2023, Niger's military-led authorities nationalised the local subsidiary of Orano, as part of a wider pivot away from Paris and towards alternative allies such as Russia.

Orano, which is 90 percent owned by the French state, has already launched several legal proceedings of its own against Niger, accusing the junta of confiscating its assets in the unrest-hit country.

Announcing the countersuit on Wednesday, the junta's Justice Minister Alio Daouda accused the French firm of "creating an ecological disaster in Niger".

Daouda lamented Nigerien land "contaminated by mining" and "toxic waste... dumped in the open air", with "nearly 400 barrels containing radioactive waste, a highly toxic material" discovered at one Orano site.

"Niger has decided to initiate legal proceedings against Orano... before national and foreign courts in order to obtain a conviction and reparations for the damage suffered," Daouda said.

Months after decreeing the forced nationalisation of Somair, Orano's Nigerien subsidiary, Niger's junta announced in November that it wished to sell the uranium produced by the mines formerly run by the French company on the international market.

A few days later, Orano warned that a shipment of at least 1,000 tonnes of yellowcake, or concentrated uranium, had left the Arlit mine in northern Niger, previously split between the French group and the Nigerien state.

The radioactive cargo has been blocked for several weeks at Niamey airport, the scene of a jihadist attack on the night of January 28 to 29 claimed by the Islamic State group.

Orano has recently vowed to pursue its legal action against Niger, as well as "anyone who wishes to get their hands on" the blocked uranium stockpile, which it values at 300 million euros ($354 million).

Uranium was first discovered in Niger in 1957 under French rule, with mining beginning in 1971.

The country produced 3,527 tonnes of the radioactive metal in 2023, equal to 6.3 percent of global production, according to mining industry publication Globaldata.