The development was announced in a video, which was obtained by The Associated Press. It says that Mullah Emdadullah Mansoor was named leader of the faction known as Mahaaz-e-Dadullah at a gathering Monday in southern Zabul province.
The meeting was attended by tribal and religious leaders, as well as the group's local commanders.
The video shows Mansoor accepting the leadership position among a crowd of gunmen. He is the nephew of Mullah Mansoor Dadullah who was killed in Khak-e-Afghan district of Zabul last year, fighting with rival Taliban.
Mansoor promised to "fight foreign forces" and exact revenge for the group's slain leader.