PARIS - A French citizen was killed in the operation to rescue hostages held by Islamist militants at a gas field in Algeria, French Foreign Minister Laurent Fabius said Friday.

The French national, Yann Desjeux, lost his life and three other French citizens were saved, French channel iTELE quoted the minister as saying.

Earlier Friday, French Prime Minister Jean-Marc Ayrault said the Algerian military operation against Islamist militants that hold dozens of foreigners was under way.

French Interior Minister Manuel Valls said Friday morning two French hostages managed to escape form their captors while French officials had no information about two other presumed French captives.

Algeria conducted an assault against the Islamist militants on Thursday during which 600 Algerian workers and four foreigners were freed.

Reports of casualties resulting from the attack have so far been confusing, with some claiming that dozens of hostages and their captor were killed in the operation.

Al-Qaida linked militants took dozens of foreign nationals hostage Wednesday night at the In Amenas gas plant in the southern Algerian desert. The hostage-takers said they were retaliating against the French military intervention against rebels in neighboring Mali.