Orano had already decided in October to suspend production in Niger owing to what it termed increasingly difficult operating conditions and financial issues.

Orano holds a 64.3 percent stake in the local mining company, Somair, while the share of the Nigerien state stands at 36.6 percent.

"For several months, Orano has been warning of the interference that the group has been suffering in the governance of Somair," the French group said in a statement.

"The decisions taken at the company's board meetings are no longer being applied and, as a result, Orano is today confirming that the Nigerien authorities have taken operational control" of Somair, it said.

In June, the junta withdrew Orano's permit to exploit one of the largest uranium deposits in the world, Imouraren, which holds an estimated 200,000 tonnes of the heavy metal.

The ruling junta, which took power in a coup in July last year, says it will revamp rules regulating the mining of raw materials by foreign companies in what is the world's seventh-largest uranium producer.