Azadi Radio described Hezb-i-Islami as playing a mediating role with the Taliban insurgents, which would be a major development if true.

A senior Afghan official in Kabul confirmed that talks in Istanbul had begun on Saturday and were to continue through Monday. He said representatives of the Taliban were present, but described them as “unofficial.”

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.