The 16-minute message said that the reports had been deliberately spread to create divisions in the Taliban.
“I am among my people. This incident never happened and it is not true. This is propaganda of the enemy,” the man speaking on the message said.
It was not possible to verify whether the voice was really Mansour’s.
The statement followed days of uncertainty over the fate of the Taliban leader, after multiple reports said he had been badly wounded in the shootout at the home of another commander in Quetta, western Pakistan, late on Tuesday.
Several senior sources within the Taliban on Sunday cast doubt on the authenticity of the audio message.
Doubts continued to linger among the group’s senior ranks, who are distrustful of their leadership following a two-year cover-up of the death of the Taliban’s founder and first leader Mullah Omar.
Mawlawi Hanifi, a commander based in southern Helmand province, said: “I listened to the clip and it looks fake.”
“I think his voice has been mimicked. Mansour himself fooled us for two years, how can we trust this now?”
Another senior Taliban source said that the group is buying time to select a new leader and bring their organisation out of “this sudden shock”.
“We need more proof,” he concluded.
Two other senior officials expressed similar concerns, with the latter insisting that Mansour succumbed to his injuries on Thursday.
In the message, a man purporting to be Mansour said: “I have recorded this message to let everyone know that I am alive.”
But two other Taliban officials based in Pakistan’s Quetta city said the clip was genuine and said they had been present at the recording.
“This audio was recorded yesterday by our leader Mansour, we were present. The meeting was attended by our high officials, edited, and then sent on to the media,” said one of the officials who spoke on the condition of anonymity.
Rahimullah Yousufzai, a Pakistani analyst and long-time observer of the Taliban, said the voice sounded like Mansour’s.
“I believe it is him,” he said, but added that questions would be asked over the delay in releasing the clip.
“Why did they wait almost five days to do that? If they’d done it earlier it might have been more effective,” he said.
He added that uncertainty within the ranks had been compounded by the mystery surrounding the death of Mullah Omar.