Updated

PARIS (AP) -- Authorities believe Al-Qaeda's North Africa branch could be behind the kidnapping of five French nationals and two Africans in Niger, Foreign Minister Bernard Kouchner said Friday.

No one has claimed responsibility for the kidnappings, Kouchner told Europe-1 radio, but he added: "We imagine Al-Qaeda in the Islamic Maghreb is responsible."

Kouchner said the army in Niger was on "a war footing" after the kidnappings, and that French intelligence and diplomatic services have been mobilized.

Armed assailants kidnapped the seven early Thursday near the uranium mining town of Arlit, in Niger's northern Sahara desert region. Five are French, one is from Togo and one is from Madagascar.

Officials say a man who worked for the French state-owned nuclear company Areva and his wife, and five employees of a subcontractor called Satom, were kidnapped.

The approximately 30 Areva expatriates in Arlit are all being evacuated to Niamey, the Niger capital and have the option of returning to France, an Areva press officer said Friday.

The Areva and employee and his wife were abducted about 2 a.m. from their home in a guarded residential district of Arlit, said Fleur Floquet. She said that Arlit is patrolled by some 350 state Niger security forces and Areva maintains private guards in the residential district. The Niger government has now decided to increase its security presence there, Floquet said.

France has received no ransom demands, Foreign Ministry spokesman Bernard Valero told reporters at a regular briefing. He said France urged all its nationals to leave the dangerous area of northern Niger.

"We aren't neglecting anything; we are studying everything under a magnifying glass. We are closely in contact with the Niger authorities and, especially, we are not rushing to any hasty conclusions," Valero said.

Al-Qaeda's North African affiliate has targeted French and other Europeans in previous kidnappings. It claimed responsibility for the July execution in Mali of an ailing 78-year-old French aid worker who had been taken hostage three months earlier in Niger.

Kouchner and seven European colleagues have sent a joint letter to EU Foreign Minister Catherine Ashton calling on the 27-member body to engage more deeply in the Sahel region in both security and development because "populations there must have ... another perspective than that offered by terrorists."

Al-Qaeda's affiliate in North Africa operates in the vast desert region from Mauritania to Chad. Al-Qaeda in the Islamic Maghreb grew out of an Algerian insurgency movement that officially joined with the terrorist network in 2006.

The Areva press officer said work at the mine, with some 2,500 employees, would not be hindered by the withdrawal of the several dozen expatriate staff.

The Imouraren deposit in Niger is the largest known uranium deposit in Africa, and the second-largest in the world after Australia's Olympic Dam deposit, according to the company's Web site.