Afghan President Hamid Karzai said Thursday the assassin of his top peace broker Burhanuddin Rabbani had won trust by coming to Kabul with a CD allegedly featuring a "message of peace" from Taliban leaders.
An emotional Karzai said he himself had heard the CD and believed it was an earnest attempt by the Taliban to reach out to the government's High Peace Council which Rabbani chaired.
The president's comments were his first in Afghanistan since he cut short a visit to the United States after Rabbani was assassinated by a turban bomber at his Kabul home on Tuesday.
Officials say the killer had waited at a guest house in the Afghan capital for four days to see Rabbani.
Afghanistan is observing a period of national mourning ahead of a state funeral for Rabbani in Kabul on Friday.
US ambassador to Afghanistan, Ryan Crocker, said the killing raised "very serious questions" about whether the Taliban was interested in talking peace.
Karzai told a press conference: "Before I went to New York, Stanikzai (one of Rabbani's deputies who was injured in the attack) came and said the Taliban has sent a message and a person has brought with him an audio CD...
"We saw that that message was not a message of peace, it was rather a deception... and the peace emissary was a murderer."
As Karzai spoke, Afghanistan's intelligence agency the National Directorate of Security (NDS) said it believed the Taliban's leadership body -- the Quetta Shura -- played a role in the killing, without giving further details.
"Our investigation is continuing but we know that someone named Mullah Hamidullah from the Quetta Shura was involved," said spokesman Shafiqullah Taheri. "This means that the Quetta Shura was also involved."
He added that the initial contact which led to the fatal meeting dated back to June.
The Taliban have yet to claim responsibility for the attack, with spokesman Zabihullah Mujahid insisting they cannot say anything before receiving more information about what happened.
In comments to reporters at the US embassy, Crocker condemned Rabbani's killing but insisted it would "not deter us from the task of defeating our common enemy where necessary and of finding peace where possible."
But he sounded a strikingly sceptical note on the prospects for peace talks in the wake of a killing.
Crocker said Rabbani's death "raises very serious questions as to whether the Taliban and those who support them have any real interest in reconciliation."
Rabbani's funeral is expected to draw large crowds.
As well as chairing the High Peace Council, he was Afghan president between 1992 and 1996 and a former anti-Soviet commander accused by Human Rights Watch of being implicated in war crimes that killed thousands of Afghans.
Pakistani Prime Minister Yousuf Raza Gilani flew to Afghanistan to pay his condolences to Karzai ahead of the funeral, his office said.