Areva operates a uranium mine near Arlit. A subsidiary of Vinci, Sogea-Satom, is employed as a subcontractor, according to a BBC report.  A French foreign ministry spokesman confirmed the kidnappings and said its officials were "totally mobilised".

When asked who he thought was behind the abduction, Bernard Valero told the Reuters news agency: "The security threat is so vague, so imprecise. Political terrorism is always very difficult to establish.

"For the moment we are in the first few hours. We've just had the information. There has not been any claim, so it's something that we can't really explore for the moment, but we will consider every possibility."

A spokesman for Niger's government told the AFP news agency that the other two hostages were from Togo and Madagascar and that they had been taken by an "armed group" of up to 30 men.

Laouali Dan Dahdit said the kidnappers "spoke mostly Arabic and Tamashek", a Berber language used by the desert region's semi-nomadic Tuareg people.

They were last seen heading towards Inabangaret, an important well and stopping point near the border with Algeria and Mali, he said. "A certain number of measures have been taken by the military as well as the police so that the victims and the kidnappers can be found quickly."

A Vinci spokeswoman said its employees had been working on an earth-moving project under Areva's supervision. Security had now been stepped up at the mine, she added.
A local resident told Reuters the attack took place in the middle of Arlit.

"They went to their houses and grabbed them. They knew exactly where they were - it is very worrying," he said.