The video identified four men as Taliban negotiators, but reports said that a fifth was also present. Two of the negotiators were identified as known Taliban operatives in the past, according to Sayed Akbar Agha, a former member of the Taliban now living in Kabul.
Mr. Agha said he recognized one of them from the video as Mullah Raouf Akhund, a former provincial governor for the insurgents who appeared to be leading the delegation in Istanbul. He identified another as Rahmatullah Wardak, a former Hezb-i-Islami insurgent who had defected to the Taliban, Mr. Agha said.
However, Zabihullah Mujahid, the Taliban spokesman, denied in a Twitter post that any talks involving representatives of the group were taking place.
Mohammad Akram Khpalwak, the secretary general of the High Peace Council, said that the talks in Istanbul were not official, and that any involvement by Mr. Khalili, the council’s chief, would have been personal, not official.
“This could be an informal channel trying to talk with the Taliban to convince them to participate in the peace process,” he said. “It is not an H.P.C. initiative. It is not representing the H.P.C. formally.”
But that does not mean the efforts may not be useful, Mr. Khpalwak said. “We welcome any such move by anyone provided the engagements give positive outcomes,” he added.
A spokesman for the office of the Afghan president declined to comment, but said he was unaware of any talks taking place.
If confirmed, the role of Hezb-i-Islami as a mediator with the Taliban would be a significant development in the troubled efforts to initiate meaningful peace talks with the Taliban. Although the faction fought against the Taliban and against the government previously, it was the first Afghan insurgent group to enter peace talks with Kabul, and it shares many ideological similarities with the Taliban.
No formal talks with the Taliban have ever been held, and various indirect efforts have repeatedly failed, most recently in June, in the wake of a truck bombing that killed hundreds at the entrance to the Green Zone, the diplomatic and government quarter.
In 2011, the Taliban assassinated the head of the Afghan High Peace Council, Barhanuddin Rabbani, by sending a supposed peace envoy who had a bomb hidden in his turban.
The previous year, a man purporting to be a key Taliban figure in peace talks collected tens of thousands of dollars in payments from the Afghan government before he was exposed as an impostor.