"Chadian forces in Mali completely destroyed the main jihadist base in the Adrar de Ifhogas mountains ... killing several terrorists, including leader Mokhtar Belmokhtar," the army statement on Chadian TV said, as reported by the BBC.
Weapons, equipment and 60 vehicles were seized in Saturday's assault, it added.
However, the death of the militant leader, nicknamed “Mr. Marlboro” and dubbed "uncatchable," has not been confirmed by other sources, including the French military, which is leading the offensive.
In Washington, an Obama administration official said the White House could not confirm the killing of Belmokhtar, Reuters reported.
On Friday, Chad’s President Idriss Deby said his forces had killed another al Qaeda commander, Adelhamid Abou Zeid, among 40 militants who died in an operation near the Algerian border in the same area as Saturday's assault.
Abou Zeid, whose death is yet to be confirmed by DNA evidence, is said to be second-in-command of al Qaeda in the Islamic Maghreb (AQIM).
Chad is one of several African nations that have contributed forces to a French-led military intervention in northern Mali targeting Islamist militants to force al Qaeda-linked groups out of their strongholds.
Belmokhtar, believed to have been active in political, ideological and criminal circles in the Sahara for the past two decades, gained notoriety as "Mr. Marlboro" because of his role in cigarette-smuggling across the Sahel region to finance his militant operations.
Both Belmokhtar and Abu Zeid have also been involved in numerous kidnappings.
Formerly a key leader of AQIM, Belmokhtar left the organization in late 2012 after falling out with leaders.
He lost an eye while fighting the Soviets in Afghanistan in the 1980s. He returned in 1993 to Algeria, where he joined the bloody civil war between Islamists and the French-backed Algerian military.
In the past 10 years, the 40-year-old rebel leader had raised tens of millions of dollars from kidnapping and other criminal enterprises to buy weapons and wage a holy war, the Wall Street Journal reported, citing U.S. officials.