Mullah Omar, founder of the Afghan Taliban, died of natural causes in Afghanistan, his son said in a statement calling for unity and quashing rumors about his father's mysterious death amid a leadership dispute.

The dispute within the Taliban threatens a fledgling peace process with the Afghan government and may open the way for Islamic State to expand its toehold of influence.

The Taliban in July officially confirmed Mullah Omar had been dead for more than two years, after the Afghan spy agency leaked the news. The next day, a hastily convened meeting appointed Omar's deputy, Mullah Mansour, as leader.