A deposed spiritual leader of Africa's most populous group of Muslims, former Sultan of Sokoto Ibrahim Dasuki, has died at age 93 while his son languishes in detention.

Sambo Dasuki has been detained by Nigeria's secret intelligence agency since December for allegedly diverting $2.1 billion meant to buy arms to fight Nigeria's Boko Haram Islamic extremists. Dasuki was national security adviser to former President Goodluck Jonathan. He remains detained despite three courts ordering his release on bail.

PR Nigeria news agency reports that Ibrahim Dasuki died Monday and is being buried Tuesday, apparently in his son's absence.

The elder Dasuki was appointed Sultan of Sokoto in 1988 and was deposed by a military regime in 1996. He was the great-great-grandson of the founder of the Sokoto caliphate, Usman dan Fodio.