By Will Ross
BBC West Africa correspondent
Rebels want more of the mineral profits from Niger's north
Tuareg-led rebels say they have abducted four French workers from a uranium mine in northern Niger.
In Niger's capital, Niamey, the government confirmed the kidnapping and said everything was being done to ensure the release of the hostages.
The mine is run by Areva - the French nuclear company.
Rebels from the Niger Movement for Justice (MNJ) have been calling for greater autonomy and a larger share of northern Niger's mineral wealth.
The MNJ said on its website that the French workers had been kidnapped in order to send a warning to foreign mining companies.
The rebels said the workers were in no danger and they were willing to hand them over to the Red Cross.
State of emergency
For several months, northern Niger has been in a state of emergency and cut off from the rest of the country.
The government recently promised to provide military protection for the uranium mines and oil installations.
There have been frequent clashes between the MNJ and the army but the government has ruled out talks with the rebels unless they first disarm.
With the demand for nuclear fuel increasing, the price of uranium has shot up and Niger's resource is in great demand.
In the past France had a monopoly on the uranium mines, but recent contracts have been signed with several other countries, including China.
The insecurity in northern Niger will worry investors, who may be forced to pay more attention to the concerns of the local population.
There is growing concern over general instability in the Sahel - the area on the fringes of the Sahara desert which includes northern Niger.
A Tuareg-led rebellion is also being fought in north-east Mali.
The United Nations recently described the combined problems of climate change, the conflict over resources and the trafficking of drugs, arms and humans as a lethal cocktail in the Sahel.