Areva's Anne Lauvergnon and Niger's Mamadou Tandja attended a ceremony
Work on what will become the world's second largest uranium mine has begun in the west African state of Niger.
After it opens in three years' time the $1.5bn (£1bn) mine is expected to yield 5,000 tonnes of uranium per year.
French nuclear energy company Areva is building the mine and will take a majority share in it.
Niger is one of the world's poorest countries and the export of uranium provides one of its few sources of foreign currency.
The open pit mine at Imouraren will employ 1,400 people and more than double Niger's current uranium exports.
The mine is in the north of Niger, home to the semi-nomadic Tuareg people.
For the past two years armed rebel groups from the region have been fighting the government for a greater share of Niger's uranium wealth.
Niger's President Mamadou Tandja made his first trip to the north since the rebellion started to lay the first stone at the mine, and on Sunday evening he met rebel leaders in the town of Agadez.
The president promised an amnesty to those who laid down their weapons.
Activists from the local environmental group Agrimane have been complaining about potential pollution from the mine and what they call the forced displacement of local people.
But the BBC's Idy Baraou in Agadez says both the government and Areva have promised to deal with such complaints
Areva director Anne Lauvergnon and France's junior Minister for Co-operation Alain Joyandet also attended the inauguration.
Areva and Niger signed an agreement in January for the firm to operate the mine, describing it as "the biggest in Africa and the second largest in the world".
France keeps close ties with its former colony and uranium from Niger is vital to its nuclear energy programme.
Areva already has other mines in the landlocked sub-Saharan country.
Other than uranium mining, Niger's population relies on subsistence farming and livestock production.
But the fluctuating world price in uranium has brought repeated instability to the country's economy.
Niger is the world's fourth biggest producer of uranium after Canada, Australia and Kazakhstan, according to the British Geological Survey.