DAKAR, Senegal -- The general commanding troops from Chad in a French-Chadian antiterrorist operation in northern Mali said Sunday that he could not yet confirm the death of a principal Islamist leader, Mokhtar Belmokhtar, a day after his government announced it on Chad's national television.
"It's still conditional," said Gen. Oumar Bikomo, speaking from the mountainous area of northern Mali where dozens of radical Islamist fighters are believed to be holed up. "I can't confirm it." The region, the Adrar des Ifoghas, has been the scene of tough combat in the past few days, spokesmen for the French and Chadian armies said, and it was in one of those engagements that Mr. Belmokhtar may have been killed.
Chad's soldiers attacked and destroyed a major base of the Islamist fighters on Saturday morning, General Bikomo said, killing about 60. One of them might have been Mr. Belmokhtar, the man who commanded a deadly raid on the gas-processing complex in the Algerian desert in January.
"We can't really identify who was who," said General Bikomo, speaking of the raid. "It is certain that some leaders were killed. But I can't confirm that Mokhtar Belmokhtar was killed. I can't tell you that he's been killed."
He said he was unsure why the death of Mr. Belmokhtar, who was for years a principal leader in Al Qaeda's regional franchise in the Sahel until he formed a breakaway group last year, had been announced by another general on Chadian television in the capital, Ndjamena.
"A lot of people died, and I can't tell you if he's one of them," General Bikomo said. "Even this morning people died. We've been fighting, we reached their base, and we destroyed it. It was our main objective."
General Bikomo was more certain about the death of a prominent leader of Al Qaeda in the Islamic Maghreb, Abdelhamid Abu Zeid, which was announced by the president of Chad on Friday. "He should be dead, yes," the general said. "One of the prisoners of war we took told us that he is dead."
On Monday, there were further indications that Mr. Abu Zeid had been killed last week in the same region of northern Mali, in the Adrar des Ifoghas mountains. A Mauritanian news site, Sahara Media, which has close contacts with Mr. Abu Zeid's group, cited an Islamist source as confirming that he had been killed in a French air strike.
But the same unnamed source denied reports of Mr. Belmokhtar's death, saying that he was alive and operating to the southwest, close to the Malian town of Gao.
France's chief of the defense staff, Adm. Édouard Guillaud, told Europe 1 radio Monday morning that he was "extremely cautious" about reports of Mr. Belmokhtar's death, but that it was probable that Mr. Abu Zeid had been killed. "It is likely, but only likely," he said. "We don't have any certainty for the moment. It would be good news."
Mr. Abu Zeid is said to have abducted more than 20 Western hostages since 2008 for ransom, some of which went to the Qaeda group. He is believed to have killed a British hostage, Edwin Dyer, in 2009 and a 78-year-old Frenchman, Michel Germaneau, in 2010. His death would raise questions about the fate of seven French hostages he is thought to have been holding in mountainous northern Mali.
The combat between the French-Chadian forces and the militants has been particularly intense over the past several days.
On Saturday night a French parachutist was killed in a firefight, the third French soldier killed since the start of France's Mali offensive in January. He was in a rugged valley with other French troops and "most of the fighting is occurring at very close range," the French military spokesman, Col. Thierry Burkhard, told reporters in Paris on Sunday.
The soldier, Sgt. Cédric Charenton, 26, was killed "in one of the most violent engagements" since the start of the French intervention, Defense Minister Jean-Yves Le Drian said on his Twitter account.
Sergeant Charenton's unit was assaulting an enemy position, Colonel Burkhard said, and "a certain number of terrorists were dug in, and it's from that position that the shots were fired." About 15 Islamist fighters were killed in the operation, the colonel said.
French losses have been small compared with those of Chad, which has already lost several dozen men. But military experts on the region say Chadian forces have a history of taking heavy losses in their operations.
"They charge in, and take a lot of casualties," said a Western defense attaché in Bamako, Mali's capital. "But they kill a lot. And they have killed a hell of a lot."
"The bad guys have been there since 2001," the attaché said. "They have trenches, defensive positions, bunkers, stored food."
They know the terrain "inside and out," he said, and are "continuing to engage the French and the Chadians on the battlefield."
Mali's forces, meanwhile, are well to the rear and are not engaged in the fierce combat in the northern mountains. The Tuareg rebel movement, which currently exercises de facto political control over Mali's north and fiercely opposes the Bamako government, has demanded that Malian troops stay out of the region. Although that demand has provoked considerable grumbling among the Malians, the French have tacitly accepted it.
Steven Erlanger and Maïa de la Baume contributed reporting from Paris.
This article originally appeared in The New York Times.