Mullah Akhtar Mohammad Mansour has been named the leader of the Taliban as the terrorist organization grapples with peace negotiations-related infighting that has triggered defections to the growing Islamic State (ISIS/ISIL) group.

Mullah Mansour is reportedly not well liked by some high-ranking Taliban commanders.

Some of those commanders have accused him of being behind the death of Taliban leader Mullah Mohammed Omar, who reportedly died of an illness.

Sirajuddin Haqqani has reportedly been named as Mullah Mansour’s deputy. He is the son of Jalaluddin Haqqani, founder of the Haqqani Network, which is considered the most lethal insurgent group targeting U.S. and international forces in Afghanistan.

Pakistan’s GEO TV, citing unnamed “well-informed” people, reported that the Taliban’s supreme council, made up of the most powerful members, “unanimously” chose Mullah Mansour, when it met in the Pakistani city Quetta this week, to replace Mullah Omar, whose death in 2013 was finally confirmed by the Afghan government and the group itself early this week.

However, BBC reports that “The naming of Mullah Mansour as Taliban leader was far from unanimous and followed days of intense debate.”

“Sources close to the movement’s leading council, or shura, say many senior commanders and other Taliban heavyweights were dismayed by the decision,” it adds.

Mullah Qaum Zakir, the Taliban’s top military chief, is among the senior commanders who reportedly disapprove of Mullah Mansour as the group’s leader.

Letters intercepted by Afghan intelligence and written nine months ago by Mullah Zakir and his counterpart Mullah Mansour Dadullah accuse Mullah Mansour of being behind his predecessor’s death and urge Taliban members to rebel against the new leader, reports The Independent. Mansour was the Taliban leader’s deputy at the time.

Various news outlets have noted that Mullah Mansour supports peace negotiations between the Taliban and the Afghan government, which were postponed following the announcement of Mullah Omar’s death.

The leader’s confirmed demise has threatened to break the Taliban into rival groups: those who support peace talks, and those who do not.

Meanwhile, ISIS has benefited from defections triggered by infighting among Taliban factions over the peace negotiations.

Continued disagreements over whether Mansour should be the leader could push more Taliban members into ISIS’ rank.

According to the Afghan Biographies website, the newly appointed Taliban leader was born in 1960 in Afghanistan’s Kandahar province, the birthplace of the Taliban located along the country’s border with Pakistan.

Mullah Omar fathered the Taliban in the 1990s.

Hasibullah Fawzi, a senior member of Afghanistan’s High Peace Council, told Bloomberg news that Mansour developed a relationship with Pakistani intelligence, which he still maintains, when he fought against the Soviet occupation of Afghanistan in the 1980s.

The move to appoint Sirajuddin Haqqani as Mullah Mansour’s deputy “was seen as an attempt to avoid infighting between Mullah Mansour and Haqqani,” reports The Independent. 

Sirajuddin is credited with leading terrorist operations for the Haqqani Network in Afghanistan.