“Areva has invested something like 1.5 billion euros [almost $2 billion] in the new mine in Niger. That is a very key area, and I think France will be very keen to maintain its long-term interest and its long-term security in that area," he said.

France has deployed Special Forces alongside Niger's army to protect the mines.

The May attacks follow the assault in January on a gas plant in Algeria. Thirty-nine foreign workers were killed by militants linked to al-Qaida. The plant has yet to reopen.

Fears that Western-run facilities in the Sahel present terror groups with easy targets are over-simplified, says Paul Melly of the London-based policy institute Chatham House.

“On the whole, the security risk is less one of fixed sites, and it's more one of generalized instability and the dangers to the survival of the stable constitutional states in West Africa and the normal process of economic development and political security," said Melly.

Melly says those concerns underpinned France’s military intervention to oust Islamist forces from northern Mali.

“For Europe, West Africa is a long-term fundamental strategic interest rather like Mexico, Central America and the Caribbean are for the U.S. It’s that kind of long term investment in partnership that really matters and that’s what underlay the decision to go so far as to send 4,000 troops into Mali," he said.