President Nicolas Sarkozy vowed on Monday that France would avenge the murder of a 78-year-old aid worker who was kidnapped and killed in the Sahara desert by Al-Qaeda's North African wing.
"I condemn this barbarous act, this odious act which has put an end to the life of an innocent man who was there to help the local population," the French leader said in a terse televised address.
Sarkozy was speaking after Al-Qaeda in the Islamic Maghreb (AQIM) declared it had killed the hostage in revenge after French and Mauritanian soldiers stormed one of the group's camps and killed six militants.
"Dear compatriots, this crime committed against Michel Germaneau will not go unpunished," he added, warning French nationals to avoid all travel to the arid region running through Mauritania, Mali, Niger and southern Algeria.
"We demand instantly of our countrymen that they abandon absolutely all travel in the Sahel zone," he said, adding that AQIM had previously killed a British hostage and has "no respect for human life."
"Far from weakening our determination, this death has reinforced it."
He said he had asked Prime Minister Francois Fillon to meet senior lawmakers to brief them on France's plans.
Foreign Minister Bernard Kouchner was sent to West Africa to tour the capitals of France's former colonies there to study security measures to protect French expatriates from further reprisals.
"More than ever we are determined to fight terrorism in all its forms and to support the countries that have the courage to combat this barbaric terrorism," he promised.
Sarkozy confirmed that Fench soldiers had taken part in last Thursday's deadly raid into Mali, in which Mauritanian and French forces killed six Al-Qaeda militants but failed to find any trace of Germaneau.
He was speaking after an emergency meeting at the Elysee Palace in Paris between Sarkozy, Fillon, key ministers, military top brass and the heads of France's domestic and foreign intelligence.
AQIM took responsibility for the killing in an audio message broadcast by the Arab satellite TV network al-Jazeera at the weekend.
"We announce that we executed the French hostage Michel Germaneau on Saturday July 24, 2010, to avenge the killing of our six brothers in the cowardly French raid," AQIM chief Abu Musab Abdul Wadud said.
"Sarkozy failed to free his compatriot in this operation but he has without any doubt opened for his people and for his country one of the gates of hell."
Some French officials have questioned details of the claim, indicating privately that the hostage might have been killed several weeks ago, but there is no doubt that Germaneau is dead.
He was seized in Niger where he had been building a school on April 19. On May 14, his abductors issued a photo of an exhausted-looking Germaneau and a taped message in which he appealed to Sarkozy to work for his release.
He said he suffered from a serious heart illness and had no more medication and that he was struggling with the heat.
Germaneau's Algerian driver was later released. He said the Frenchman was being held in a desert zone in Mali.
On July 11, AQIM gave France a 15-day deadline to help secure the release of its members in the region.
Last Thursday, with the ultimatum just days away, between 20 and 30 French soldiers took part alongside Mauritanian forces in a raid on a remote militant camp in the Malian desert.
Germaneau was working with Enmilal, a small French aid agency, to improve health services and schools in Niger.
AQIM is also holding two Spaniards in the region after kidnapping them more than seven months ago: Albert Vilalta, 35, and 50-year-old Roque Pascual.
The group has also been blamed for the murder of British hostage Edwin Dyer, 60, who was kidnapped by Islamic extremists in the Sahel region bordering the Sahara desert in January 2009.