Afghanistan's president Hamid Karzai has pushed past the 50% threshold needed to avoid an election runoff, but a UN-backed watchdog says it has found clear evidence of fraud and ordered a partial recount.
Returns released on Tuesday from almost 92% of polling stations have Mr Karzai ahead with 54.1% percent of the vote to 28.3% for his main challenger, former foreign minister Abdullah Abdullah.
It was the first time the Independent Election Commission had reported Mr Karzai on course to exceed the threshold needed to win outright and avoid a second round.
The results are final only after they are certified by the Electoral Complaints Commission (ECC), a separate body led by a Canadian and mainly appointed by the United Nations.
In a statement, it said it had found "clear and convincing evidence of fraud in a number of polling stations."
The EEC ordered the Independent Election Commission to recount results from polling stations where one candidate received more than 95% of the vote or where more votes were cast than the expected maximum of 600.
Most of the stations where it found fraud had either a larger than expected number of total votes cast, or a higher than expected proportion cast for a single candidate, it said.
The Independent Election Commission said it was already fighting fraud and had set aside results from more than 600 of the country's 25,000 polling stations because of concerns over irregularities.
Some suspicious results posted earlier, including from a village where Mr Karzai received every single vote cast including exactly 500 at each of four separate polling stations, were removed from the commission's web site without explanation.
Commission member Daoud Ali Najafi said it could take two to three months to comply with the ECC's order. A second round, if needed, would be difficult to hold in Afghanistan beyond the end of October because of extreme weather.