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By Mushtaq Yusufzai and Fazul Rahim

PESHAWAR, Pakistan — The Afghan Taliban was locked in a tense leadership battle on Monday, raising the specter of violent clashes within the group that could derail efforts to negotiate an end to the country’s insurgency.

Picture purportedly shows Mullah Akhtar Mohammad Mansoor, who was named leader of the Afghan Taliban on July 30, 2015. The image was provided by a senior Taliban figure on condition of anonymity because he was not authorized to release it. Its authenticity could not be independently verified by NBC News.Taliban handout via Reuters

Relatives of deceased one-eyed leader Mullah Omar challenged the group’s newly appointed emir, Mullah Akhtar Mohammad Mansoor.

According to a rival group led by Omar’s younger brother Mullah Abdul Manan, Mansoor had essentially appointed himself head of the militant group without winning the support from the movement’s religious leaders and key commanders.

Omar’s family wanted any successor be from within his clan. Omar's son, Maulvi Mohammad Yaqoob, was the leading contender of this faction, commanders told NBC News.

"It was a great surprise and shocking news to all of us gathered for mourning and condolence of the death of ... Mullah Mohammad Omar when someone stood and started introducing Mullah Mansoor as the new emir," Manan told NBC News on the telephone from an undisclosed location. "This was not way of choosing the new emir."

"We pray that we do not have to fight our Muslim brothers, but the situation is very tense and a confrontation is highly possible"

Mullah Hasan Rahmani, a former deputy to Omar who is now the head of Taliban’s political council, told NBC News that "Mullah Mansoor had gotten himself appointed as emir from his own group." He also spoke on the telephone from an undisclosed location.

Already tensions were surfacing between rival groups on the battlefield, according to a commander who spoke to NBC News.

“Soon we will go after those Taliban who have lost their way and accepted this puppet as the new leader,” said the commander, who accused Mansoor of being a stooge of neighboring Pakistan.

“We pray that we do not have to fight our Muslim brothers, but the situation is very tense and a confrontation is highly possible,” the commander in the southern province of Helmand told NBC News on condition of anonymity.

However, another top fighter in Kunduz province in northern Afghanistan told NBC News he welcomed Mansoor’s leadership.

“We are hearing from here and there that Mullah Omar’s son and brother are not happy with this appointment, but the fact is that Taliban is not like a monarchy to be inherited by family members,” said the senior commander who also spoke on condition of anonymity.

Yaqoob was too young and lacked the experience to lead the militant group, he added.

Mullah Omar is seen in this undated U.S. National Counterterrorism Center image.National Counterterrorism Center / Reuters

Local news service Khaama press reported that fighters had clashed in the western province of Herat over the succession battle.

The divisions could endanger nascent official peace talks with the government aimed at ending the group’s violent 14-year insurgency.

The government of President Ashraf Ghani issued a statement Monday saying it was keeping an eye on reports of infighting.

“The government of the Islamic Republic of Afghanistan closely monitors the new developments in the Taliban leadership and the Haqqani network,” the statement read, referring to the Taliban and closely linked fighters with bases in Pakistan.

A high-ranking Afghan intelligence official told NBC News that while the rivalry between factions could actually strengthen the government’s position, it could also inflame violence by emboldening fighters who had defected from the Taliban to join ISIS.

"Although it is to our advantage, we are also worried that it may provide [ISIS] the opportunity to exploit the situation," the official told NBC News on condition of anonymity.

Mourner offer funeral prayers for Taliban leader Mullah Mohammad Omar at a mosque in Peshawar, Pakistan, on July 31.Mohammad Sajjad / AP
F. Brinley Bruton contributed.