The Afghan government is investigating reports of the death of Taliban supremo Mullah Omar, a presidential spokesman says, amid frenzied speculation about the rumoured demise of the reclusive warrior-cleric.

The insurgents have not officially confirmed the death of Mullah Omar, who has not been seen publicly since the 2001 US-led invasion of Afghanistan that toppled the Taliban government in Kabul.

Rumours of his ill-health and even death have regularly surfaced in the past. The reports come just two days before a second round of peace talks between insurgents and the Afghan government is scheduled.

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Wednesday’s announcement from spokesman Sayed Zafar Hashemi came after unnamed government and militant sources told media that the one-eyed leader died two or three years ago.

“We can confirm that Mullah Omar died two years ago… in Pakistan due to an illness,” a separate official in Afghanistan’s national unity government told AFP.

“He was buried in Zabul province (in southern Afghanistan),” said the senior official, citing Afghan intelligence sources.

Hashemi told a press conference: “We have seen reports in the media regarding the death of Afghan Taliban leader Mullah Omar.

“We are investigating these reports… and will comment once the accuracy of these reports are confirmed.”

If confirmed, Omar’s death would mark a significant blow to an almost 14-year insurgency, which is riven by internal divisions and threatened by the rise of the Islamic State group in South Asia.

The Taliban in April published a descriptive biography of the “charismatic” supreme leader, in a surprise move apparently aimed at countering the creeping influence of the Islamic State group within their ranks.

The Taliban have reportedly seen defections to the Islamic State in recent months, with some insurgents expressing disaffection with the low-profile leader Omar.

The biography, posted on the Taliban’s official website to commemorate Omar’s apparent 19th year as supreme leader, described him as being actively involved in “jihadi activities” – trying to dispel speculation that he had died.

And earlier this month in a message released in Omar’s name, the leader was quoted as hailing the peace talks as “legitimate”.

The comments, the first reputedly made by Omar on the nascent dialogue, eased concerns at the time that the process lacked the leadership’s backing.

A member of the Quetta Shura, the Taliban’s governing council, voiced doubt over whether that message – released just before the Muslim festival of Eid-ul-Fitr – was from Mullah Omar himself.

“For the last few years he has not attended any big gathering, neither has he sent any audio message to his followers,” the member, who requested anonymity, told AFP on Wednesday.

“That gives us reason to believe that he has died.”