Taliban fighters train with their weapons in an undisclosed location in Afghanistan, July 14, 2009. Reuters/Stringer

Just months after the Afghan Taliban appointed its new leader, and weeks after the group experienced a major battlefield success, leaders critical of Mullah Akhtar Mansoor said they would be holding a meeting within days to discuss selecting a new leader, Reuters reported Tuesday. It was unclear how much power anti-Mansoor factions within the Taliban held, and there were fears that an internal rift could create space for militants affiliated with the Islamic State group, also known by ISIS, to make gains in Afghanistan.

“There is one agenda, and that's to choose the new emir (leader) unanimously and get rid of Mullah Mansoor,” Mullah Abdul Manan Niaza, a spokesperson for the anti-Mansoor faction, said, according to Reuters.

Mansoor became head of the Afghan Taliban in late July, following the revelation that Mullah Omar, the Taliban’s founder, had been dead for two years. Mansoor issued a statement in Omar’s name calling for unity, which effectively sealed his appointment as leader. Some commanders considered the move deceitful and refused to accept him, believing that Omar's eldest son should have succeeded his father.

Analysts speculated the recent takeover of the northern Afghanistan city of Kunduz had cemented support for Mansoor. The battlefield victory marked the Taliban’s first occupation of a city since the militants were ousted from power in 2001. The Taliban was forced out of the city last week amid intense NATO airstrikes.

Mansoor has been part of the Taliban’s core leadership since its early days and reportedly maintained a close relationship with Omar. The rift within the Taliban has postponed peace talks between the group and the Afghan government. At the same time, ISIS has grown in Afghanistan. Some fighters disgruntled with the Taliban have reportedly defected to the Syria-based militant group, which has made significant inroads in the country in recent months.

President Barack Obama announced last week that U.S. forces would remain in Afghanistan beyond the planned withdrawal date, as Afghan forces still lacked the ability to combat insurgents on their own.