Afghanistan's troubled presidential election plunged deeper into crisis on Sunday when one of the main contenders accused a deputy of President Hamid Karzai of orchestrating fraud in favour of his rival.
Supporters of Abdullah Abdullah, a former foreign minister, released an audio recording they said was vice president Mohammad Karim Khalili encouraging vote-rigging in favour of Ashraf Ghani, the other contender in the race.
Khalili's and Ghani's staff dismissed the recording as a fake.
Allegations of mass fraud have shadowed the outcome of the vote, which was meant to be the first democratic transition of power in Afghanistan's history ahead of the withdrawal of international combat troops at the end of this year.
The 8 million votes cast in the second round of the election, held in June, are currently being audited under UN supervision, according to a deal brokered by the United States.
The audit has also been dogged by delays as Abdullah and Ghani have not been able to agree on some technicalities, such as how to disqualify votes.
The recording released on Sunday is the most recent that Abdullah's campaign alleges is evidence of high-level collusion in an effort to ensure Ghani, a former finance minister and World Bank technocrat, is declared the winner.
The speaker allegedly encourages cheating at the highest level of the administration to help Ghani win.
"I am aware that in all efforts within the government and within the electoral commissions and with his Excellency the President of Afghanistan there exists an agreeable perception of the victory of this team and this candidate," the speaker says after referring to one of Ghani's running mates, Sarwar Danish.
In what is purportedly an address to close political associates before the June 14 run-off, the speaker is heard saying: "The election outcome must turn in favour of this team... even if these means are against electoral mechanisms."
Abdullah's team did not say where the speech was delivered, or how the recording was obtained. Its authenticity could not be independently verified by Reuters.
Karzai's office said it had no immediate comment.
Both Khalili's and Ghani's staff said the tape was fake.
"The audio is completely fake ... Khalili does not speak like that," said Abbas Basir, chief of staff for Khalili. "Our rival team is resorting to such an act because they are under immense pressure," he added.
Results from early counting, which was halted by previous allegations by Abdullah of vote rigging, showed Ghani leading with a substantial majority.
The auditing process re-started on Sunday after a week-long delay, but Abdullah's team boycotted the process.
Karzai has said the audit will be completed by the end of the month, but diplomats worry it could be months before Karzai's replacement is known. Afghanistan had been due to swear in a new president at the weekend.
The delay complicates the signing of two agreements that would allow the United States and Nato to maintain a small military presence in Afghanistan for training and counter-insurgency operations.
Karzai has refused to sign the security deals, but both Ghani and Abdullah say they will enact the pacts.