"Mansour was seriously injured. He was rushed to hospital and we are not sure if he survived his wounds," Sultan Faizi, the spokesman for the Afghan first vice president, told AFP.
An Afghan intelligence source confirmed his account, and insurgent sources also told AFP that Mansour had been injured.
Taliban spokesman Zabihullah Mujahid denied that any such firefight took place.
Mansour was announced as the new Taliban chief on July 31, after the militant movement belatedly confirmed the death of Mullah Omar, who led the Islamist movement for some two decades.
But splits immediately emerged in the Taliban following his appointment, with some top leaders refusing to pledge allegiance to him, saying the process to select him was rushed and even biased.
Four people were killed in the firefight Wednesday, a Taliban source close to Mansour's group told AFP, and a number of people injured.
"Akhtar Mansour is among the injured but the extent of his injuries is not clear," he said.
"The meeting was at the home of Abdullah Sarhadi, a commander in Mansour's group and a former Guantanamo Bay prisoner who had been arrested after 2001 by the US, then released, the Taliban sources said."
His account was confirmed by another Afghan Taliban source.
He was arrested again later on by Pakistan, then released sometime in 2012, they said.
"There were differences on some points which later turned into harsh words, then Sarhadi opened fire and the others returned fire," the Taliban source said.