Called the Prince by his entourage, he was considered the last major surviving figure among the jihadists in North Africa. All the others have been killed in French raids. He is certainly the most feared among them because of his operational and planning skills.

Born in Algeria, he fought in the Algerian civil war of the 1990s. He joined a militant group based in Algeria and took up smuggling and kidnapping for ransom; one terrorist raid included the abduction of a Canadian diplomat in late 2008.

Mr. Belmokhtar’s success in maneuvering largely unhindered for years in the deserts of northern Mali and southern Algeria and Libya was a result of his masterful integration into the local populations. He married a woman from Timbuktu, Mali; spoke the local dialects; and shared some of his rich takings from more than a decade of kidnapping Westerners.

The Canadian diplomat, Robert Fowler, a former United Nations special envoy, was released after four months. He said in a 2013 interview, “I was always impressed by the quiet authority he exhibited.” Mr. Fowler met with Mr. Belmokhtar several times during his captivity in the desert.

Among his militant names is Laaouar, or the One-Eyed, because it is said he may have lost an eye while fighting the Soviets in Afghanistan, where he learned combat skills. A major cigarette trafficker, he is also known as Marlboro Man.

Mr. Belmokhtar became a leading figure in Al Qaeda in the Islamic Maghreb, or A.Q.I.M., the Qaeda affiliate in North Africa. He was the most experienced of four leaders of Al Qaeda in the Islamic Maghreb until he broke with the group to lead Al Mulathameen Battalion, which was officially designated as a foreign terrorist organization by the State Department in 2013.

In January 2013, Mr. Belmokhtar led the attack on a gas plant in Algeria that resulted in the death of 38 civilians, including three Americans. Four months later, his group joined with a West African terrorist faction — the Movement for Oneness and Jihad in West Africa — to carry out attacks in Niger that killed at least 20 people, the State Department said.