Armed forces in Chad claim to have killed Mokhtar Belmokhtar, the commander of an al-Qaida-linked brigade which carried out a bloody assault to take western hostages at a gas plant in Algeria in January.

Belmokhtar died in a raid on an Islamist rebel base on Saturday, according to a military spokesman.

One of the world's most wanted terrorists, he had claimed responsibility for the strike on the In Amenas gas plant in which more than 60 people were killed after troops stormed the complex on 19 January.

In a statement read out on Chadian television, armed forces spokesman General Zacharia Gobongue said: "Chadian armed forces operating in northern Mali completely destroyed a terrorist base … The toll included several dead terrorists, including their leader Mokhtar Belmokhtar."

Belmokhtar's death, if confirmed, would be a major blow to Islamist rebels in northern Mali who have been pushed into their mountain strongholds by French and African forces.

The report of his death comes days after Chad's president, Idriss Deby, said soldiers in Mali had killed another leading al-Qaida commander in the Sahara, Adelhamid Abou Zeid. French officials said they could not confirm the killing of either Abou Zeid or Belmokhtar.

Chad is among several African nations that have contributed forces to a French-led military intervention in Mali aimed at ridding its vast northern desert of Islamist rebels who seized it nearly a year ago, following a coup in the capital. Britain has provided logistical support to the military operation.

Western and regional nations are worried that al-Qaida will use the zone as a launchpad for international attacks and strengthen ties with homegrown Islamist groups, such as al-Shabaab in Somalia and Boko Haram in Nigeria.

In a speech on Friday, French president François Hollande said the Mali operation was in its final stage: "Terrorist groups have taken refuge and are hiding in an especially difficult zone."

Belmokhtar, nicknamed Mr Marlboro because of his involvement in cigarette smuggling, was born in Algeria in 1972 and claimed he gained combat experience in Afghanistan before returning to his home nation. The one-eyed gangster had also been dubbed "The Uncatchable" by French intelligence after being linked to a series of kidnappings of foreigners in north Africa over the past decade.

He was sentenced to death by an Algerian court in 2008 for the murder of 13 customs officers.

Belmokhtar began a two-decade career of Islamic militancy, first as a member of Algeria's Islamic Armed Group in the country's civil war, then as a joint founder of the Salafist Group for Preaching and Combat.

That faction evolved into al-Qaida in the Islamic Maghreb, a group as interested in kidnapping and smuggling as building an Islamic caliphate. But his relationship with the al-Qaida leadership became strained and it was announced in October that he had been relieved of his command. He later formed his own group based in Gao, Mali, called the Khaled Abu al-Abbas Brigade, which claimed responsibility for the attack on the gas plant.

His group also uses the name the Masked Brigade.

Belmokhtar was believed to have remained close to his former comrades in al-Qaida.

"He is a pirate king of the Sahara," Jon Marks, a specialist in the region at the Chatham House thinktank, said after the gas plant attack. "But like most of these Algerian groups he mixes criminality with ideology, with the balance on either aspect depending on the circumstances."