The Taliban, which ruled Afghanistan from 1996 until 2001 and has waged an anti-government insurgency since then, confirmed in July its founder had died.
It later appointed Mullah Akhtar Mansour as its new head, sparking an internal rift with Omar’s family including his son Yakoub.
Afghan intelligence sources had previously said he died in 2013 in a hospital in the Pakistani metropolis of Karachi, while there had also been rumours he may have been killed by his enemies.
The group itself later admitted covering up his death for two years, saying they had wanted to keep it secret until foreign forces ended their fight against the militants.
In an audio recording issued Sunday night, and confirmed to AFP by Afghan Taliban sources, Yakoub — who was initially reported to have been in contention to lead the group himself — said his father had died of a long-term illness in Afghanistan and was suffering from Hepatitis C.
“I assure you that when he died, he passed away from a natural death. He was not martyred either by elders inside the Emirate nor by enemies outside the Emirate,” said Yakoub, thought to be in his late twenties, in his first public statement.
“When his health took a turn for the worse, he died quickly. According to the primary information we had from the doctors, he was diagnosed with Hepatitis C.”
Yakoub added that his father had not picked a successor.
The appointment of Mullah Mansour has caused some consternation among the Taliban ranks, particularly among those who feel he is too close to Pakistan’s military establishment, the movement’s long-time backer.
Without addressing the issue of the leadership directly, Yakoub stressed upon the need for unity within the Taliban, in what could be interpreted as a softening of his stance toward Mansour.
“The most important thing for us is to maintain our unity. Not to talk ill of people, that he is perfect, he is not perfect, he has this or that defect.
“I myself accept any decision of the Ulema (Islamic scholars), and am even ready to sacrifice myself for the sake of unity. I am ready to do a suicide attack, if unity could be ensured by this,” he added.
Despite their leadership struggles, the Taliban have ramped up their attacks on the government and foreign troops. On Monday they freed hundreds of prison inmates after detonating a car bomb that killed four policemen in eastern Ghazni city.