Belmokhtar's death was announced on state television in Chad, The New York Times reported.
"Today, Saturday, at noon, Chadian armed forces on mission in Mali totally destroyed the principal base of the terrorists and narcotraffickers in the Ifoghas mountain range," Chad's military spokesman, Gen. Zakaria Ngobongue, said on national television. He said several terrorists "including the chief, Mokhtar Belmokhtar" had been killed in the operation.
Belmokhtar, 40, has been accused of being the mastermind behind the January attack on the gas plant that led to a four-day hostage crisis.
On Jan. 19, Algerian forces raided the plant, resulting in the deaths of 37 foreign hostages, including three Americans, along with about 30 militants.
U.S. officials said they were aware of the reports of Belmokhtar's death and were seeking confirmation.
Chadian soldiers have been fighting Islamist militants in Mali as part of an international force led by France.
On Friday, Chad claimed responsibility for killing Abdelhamid Abou Zeid, the second-in-command of al-Qaida in the Islamic Maghreb.