Afghan presidential candidate Abdullah Abdullah has accused senior election officials of serious fraud, opening a dispute over the vote count that could threaten a smooth transition of power.
The United Nations had called on candidates to give officials time to conduct the count and investigate fraud allegations, but on Sunday, just one day after the vote, Abdullah launched a verbal assault on the Independent Election Commission.
He said that the turnout figure of seven million voters announced by the IEC commissioner Ahmad Yousuf Nuristani was probably false.
And he demanded the sacking of Zia-ul-Haq Amarkhail, chief of the IEC secretariat, over an alleged attempt to remove unused ballots from the IEC's headquarters in Kabul on polling day.
A successful election is seen as the key test of the success of the 13-year international military and aid effort in Afghanistan, but Abdullah's salvo against the IEC could lead to months of political instability.
"There is no collaborating evidence [of the turnout figure] at all throughout the country - that is something that is questionable and what we are concerned about is once again engineered fraud," Abdullah said. "The head of the secretariat was ... caught red-handed and we want an investigation. We want him to be removed from his position."
Abdullah feels massive fraud denied him victory in the 2009 election, and he has said that only a repeat of ballot-rigging could deny him power this election.
"Allegations of fraud need to be addressed," US ambassador James Cunningham said on Saturday after polls closed.
"But the candidates and their supporters should refrain from premature judgments and from criticism that is not supported with clear evidence."
Saturday's run-off pitted former foreign minister Abdullah against ex-World Bank economist Ashraf Ghani after the two came top of the first-round election on April 5.
The preliminary result is due on July 2, before the official complaints period begins, and the final result is set for July 22.