President Nicolas Sarkozy vowed that France would avenge the murder of a 78-year-old aid worker who was abducted 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,” Sarkozy said in a terse televised address.

Sarkozy spoke 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 in Mali and killed six militants.

“Dear compatriots, this crime committed against Michel Germaneau will not go unpunished,” Sarkozy said, warning French nationals to avoid 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 the same AQIM cell had previously killed a British hostage and was planning attacks. “Far from weakening our determination, this death has reinforced it.”

In Mali, a local elected official told AFP that Germaneau had been beheaded after the raid in the presence of Abdelhamid Abou Zeid, the leader of the AQIM cell that has been blamed for killing the Briton in 2009.

“He was still alive when the raid took place, but hidden in a mountainous region in Kidal, near the Algerian border,” the local official said, speaking on condition of anonymity.

“The area is an impregnable fortress, where Islamists have planted mines and constructed bomb shelters,” he said. There was no immediate way to confirm this report, and Sarkozy did not say how he knew the hostage was dead.

Sarkozy 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,” Sarkozy promised.

Sarkozy confirmed French soldiers had taken part in last week’s deadly raid into Mali, in which Mauritanian and French forces killed at least 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 … Michel Germaneau 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 said there was no doubt that Germaneau is dead.

On July 11, AQIM gave France a 15-day deadline to help secure the release of its members in the region.

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 Roque Pascual, 50. The group has also been blamed for the murder of British hostage Edwin Dyer, 60, who was kidnapped by Islamists in the Sahel in January 2009.