Taliban sources say, Afghan Taliban leader Mullah Akhtar Mansour has been seriously wounded in shooting at a meeting of militants in Pakistan.
This incident took place when four Taliban gunmen were killed in the gunfight after an argument on the outskirts of Quetta, a source said.
Another report said Mullah Mansour died but this is unconfirmed. A Taliban spokesman denied the gunfight happened. Mullah Mansour's appointment prompted splits in the Taliban after its founder Mullah Omar's death emerged in July.
A number of senior Taliban commanders refused to pledge allegiance to him and a faction opposed to him was set up last month under Mullah Mohammad Rasool. The Taliban source said the firing seemed to be spontaneous rather than planned.
Several other Taliban sources told the BBC that Mullah Mansour and his bodyguards had been at the house of another militant, Abdullah Sarhadi, when fighting broke out. Sarhadi is a Taliban figure with symbolic importance after spending years in US detention in Guantanamo Bay, reports the BBC's Dawood Azami.
Compared to Mullah Omar, his secretive predecessor, Mullah Mansour has adopted an open approach and has met Taliban commanders regularly to discuss their policy concerns.
What prompted the shooting in Quetta is unclear, but Reuters reports that a senior Taliban commander noted that during the discussion, some senior people developed differences and they opened fire at each other but this report has been categorically rejected by Taliban spokesman Zabihullah Mujahid.
"No such incident has happened, because he is in Afghanistan not in the area of Pakistan they have mentioned. Secondly his security is not weak to allow such an incident," he told the BBC Afghan service.