A footage circulating on Twitter on Thursday, appears to show Haji Mullah Achakzai kneeling on the ground blindfolded before being executed.
The commander, based in the Badghis province near Herat in Afghanistan, was reportedly arrested by the Taliban after they seized the area.
Afghan security adviser and friend of Achakzai, Nasser Waziri, told Newsweek that the jihadist group shared the disturbing footage through a Taliban-related network.
Mr Waziri verified the footage with other government officials and police officers.
“He was surrounded by the Taliban and had no choice but to surrender last night,” Mr Waziri said.
“The Taliban targeted Achakzai because he was a high-ranking intelligence official.”
General Achakzai, in his early 60s, was a known enemy of the Taliban and fought against the group in the decades-long conflict.
The Taliban had insisted that there would be no acts of vengeance against former enemies after their takeover of the country on Saturday.
But according to Amnesty International, Taliban fights massacred nine ethnic Hazara men after they took control of the province of Ghazni in July.
According to eyewitness accounts, six men were shot while three were tortured to death in the village of Mundarakht between July 4 and 6.