NIAMEY/PARIS (Reuters) -Niger plans to nationalise the Somair uranium mine operated by France's Orano after months of worsening relations between the French state-owned company and its local partners following a 2023 coup in the West African nation.

Niger's decision to nationalise Somair comes amid a wave of mine nationalisations across West Africa, prompting concerns from global miners and other foreign investors who have invested billions of dollars into the region.

In a statement late on Thursday, Niger accused the French company of taking a disproportionate share of the mine's commercialised production compared to its shareholding.

"According to the shareholders' agreement, the uranium produced by SOMAÏR is removed by the shareholders in proportion to their respective stakes. However, the figures....are far from reflecting this sharing rule," the statement said.

Orano holds a 63% stake in Somair, while Niger's state-owned Sopamin owns the remainder, but the government said Orano had taken 86.3% of production between 1971, when the mine was launched, and 2024, without elaborating.

It also accused Orano of what it called "irresponsible, illegal and unfair" behaviour pointing to the company's decision to withdraw French nationals working on the project, disconnect it from the group's IT system, and halt production at the mine.

Orano declined to comment on Niger's plans to nationalise Somair. It did not immediately respond to a request for comment on the government allegations.

Orano has been pursuing arbitration against Niger and filed lawsuits in the country against state actions, and had warned of government interference at Somair, which it said was damaging the mine's financial situation.

It was exploring a potential sale of its stake in Somair, after Niger blocked uranium exports from the mine and took control of it, according to a Financial Times report in May.

The government seized control of the mine in December.

In neighbouring Mali, Canada's Barrick Mining had its Loulo-Gounkoto gold complex placed under state control by a court on Monday in a major escalation of a dispute over taxes and ownership.

Burkina Faso has also nationalised five gold mines this month.

(Reporting by Boureima Balima in Niamey; Additional reporting by Jean-Stephane Brousse and Dominique Patton in Paris; Writing by Ayen Deng Bior; Editing by Bate Felix, Rod Nickel and Rachna Uppal)