Taliban impostor 'dupes Afghans and vanishes with cash'
An impostor posing as a leading Taliban negotiator held secret talks with Afghan officials, report US media.
The Afghans thought they were dealing with Mullah Akhtar Mohammed Mansour, a top Taliban commander.
But he may not even have been a member of the Taliban, reports the New York Times, which broke the story.
He was paid "a lot of money", then he disappeared, say diplomatic sources. Afghan President Hamid Karzai has denied reports he met the impersonator.
The man is said to have travelled from Pakistan, where it is thought the Taliban's leadership is based, and reportedly had three meetings with government officials.
The fake Taliban leader was flown to Kabul on a Nato aircraft and taken to the presidential palace to meet Mr Karzai, unnamed Nato and Afghan officials told the New York Times.
Mr Mansour was civil aviation minister during Taliban rule, but BBC correspondents say it is not clear if Afghan officials would recognise him these days.
Doubts about the man's identity arose after someone who knew Mr Mansour told Afghan officials he did not recognise the impersonator.
"It's not him," an unidentified Western diplomat in Kabul, said to be deeply involved in the negotiations, was quoted by the newspaper as saying. "And we gave him a lot of money."
The Washington Post quoted Afghan officials as saying that the man was a lowly shopkeeper from the Pakistani city of Quetta.
During a news conference on Tuesday, President Karzai denied the meeting ever took place.
"We have not met anyone named Mullah Akhtar Mohammad Mansour. Mullah Akhtar Mohammad Mansour has not come to Afghanistan," Mr Karzai said in Kabul.
"Do not accept foreign media reports about meetings with Taliban leaders. Most of these reports are propaganda and lies," he added.
Nato's International Security Assistance Force (Isaf) in Afghanistan refused to comment on the reports.
It is not clear whether the imposter had any links to the Taliban or if he was simply a conman. Some suggest he might have been a Pakistani intelligence agent.
An Afghan intelligence official told the BBC the real Mr Mansour is a senior Taliban member in charge of weapons procurement.
He was once touted as successor to Taliban founder Mullah Omar's second-in-command, Mullah Abdul Ghani Baradar, who was arrested in Pakistan in January.
President Karzai has said that talks with the Taliban will be essential to end the nine-year war in Afghanistan, although diplomats have said meaningful negotiations are still some way away.
In many cases the government is not sure who it is dealing with or whether they have the authority to speak on behalf of the Taliban, says the BBC's Quentin Sommerville in Kabul.
Western diplomats have previously conceded that some of those claiming to represent the Taliban have turned out to be frauds.
Mullah Omar last week said rumours of talks between the Taliban and the Afghan government were a ploy by Western powers.
Nato said last month channels of communication had been open for some time, but were not yet at the stage of negotiation.
Correspondents say there have been contacts between some insurgents and the Afghan government, although not at a senior level.