Vehement denials by the Islamist group of any firefight have fallen on sceptical ears, especially after they kept the death of longtime chief Mullah Omar secret for two years.
Speculation about Mansour's fate reached a fever pitch after unconfirmed media reports on Friday claimed that he had died, even as the group vowed to release an audio message from the leader to prove otherwise.
"Our supreme leader is in a far away place where only a few trusted commanders can reach him," Mujahid told AFP.
"We are trying to get an audio message from him soon."
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The militant movement, which saw its first formal split last month, has appeared anxious to quell speculation about Mansour's fate.
Mansour was appointed leader four months ago in an acrimonious leadership transition and his death, if confirmed, could intensify the power struggle within the fractious group.
"The Taliban is suffering from a credibility crisis after they admitted to hiding Omar's death for years," Kabul-based military analyst Jawed Kohistani told AFP.
Mansour was declared Taliban leader on July 31 after the insurgents confirmed the death of Omar, who led the Islamist movement for about two decades.
But splits immediately emerged in the group, with some top leaders refusing to pledge allegiance to Mansour, saying the process to select him was rushed and even biased.
Many were also unhappy that Omar's death had been kept secret for two years -- during which time annual Eid statements were issued in his name.
A senior Pakistani intelligence official told AFP that Mansour had been "very seriously injured" in what he described as a "heavy exchange of fire" at a gathering of militant commanders near the Pakistani city of Quetta.
An Afghan intelligence official and multiple insurgent sources close to Mansour's group confirmed the account to AFP, adding that the firefight on Tuesday left at least four Taliban members dead and several others wounded.
The shootout also threatens to derail a renewed regional push to jump-start peace talks with the Taliban.