Sources, speaking on condition of anonymity, confirmed his death and said he had been transferred to a Kabul hospital on Thursday afternoon due to the severity of his wounds.
Niazi, who was reportedly shot three times in the head, was initially taken to Herat District Hospital after being seriously wounded in an apparent Taliban-on-Taliban attack.
Sources said three insurgents were killed and three others were wounded in the clash.
Provincial officials told Ariana News last week that Niazi was wounded on Wednesday in a skirmish with Taliban militants in the Guzara district of the province.
The sources stated at the time that Niazi, a pro-Taliban commander, was taken to Herat’s public hospital.
According to the sources, three of Niazi’s bodyguards were killed in the skirmish.
The Taliban has not commented in this regard.
Niazi was believed to have been Mullah Mohammad Rasool’s deputy – the head of the faction that split from the Taliban in November 2015, following the announcement in July that year that the Taliban’s longtime leader Mullah Omar was dead.
The dissident faction’s announcement was at the time believed to be the first public and official split of the Afghan Taliban since the group formed in the 1990s.
Omar’s deputy at the time was Mullah Akhtar Mohammad Mansoor, who claimed power — sparking a battle over the group’s leadership.
Rasool and Niazi were among several Taliban commanders who challenged Mansoor’s appointment as leader. Mansoor was the leader of the group from 29 July 2015 to 21 May 2016 but was killed in a drone strike by the United States in Pakistan.
Niazi was born 1968 in Pashtoon Zarghoon district, in Herat province and served as governor of Kabul Province under the Taliban regime.