Top Islamist militant leader Abdelhamid Abou Zeid has "likely" been killed in Mali as reported by Chadian forces, the French army's chief of staff, Admiral Edouard Guillaud, said on Monday.
"It is likely, but it is only likely," Guillaud said when asked on Europe 1 radio about the killing, adding that French authorities cannot "have any certainty right now because we have not recovered the body."
On the reported killing of another Islamist rebel leader, Mokhtar Belmokhtar, Guillaud was more sceptical, saying: "I am extremely cautious."
He also said the French army "has no information" about where French hostages being held in the Sahel region may currently be located. He said it was "possible" they had been moved.
He said French forces in Mali had uncovered an "industrial terrorist organisation" in the northeast, where French and Chadian troops are hunting down Islamist rebels driven from northern Mali's main cities by a lightning French-led offensive launched in mid-January.
French forces have so far found more than 50 weapons caches, a dozen workshops and 20 improvised explosive devices, he said.
Guillaud said the military operation was dealing a fatal blow to Al-Qaeda in the Islamic Maghreb (AQIM), the leading militant group in the region.
"We are breaking the back of Al-Qaeda in the Islamic Maghreb, that was the goal set by the president," he said.
He said the French military was not surprised that fighting had intensified in recent days as Islamist rebels have been cornered in mountain hideouts.
"We knew this would be the hardest part of this campaign," Guillaud said.