Results of last month's election have been released piecemeal
Latest results from Afghanistan's presidential election show President Hamid Karzai with 54.1% of the vote after 92% of polling stations declared.
The results push President Karzai past the 50% threshold needed to avoid a run-off with rival Abdullah Abdullah.
But the figures were thrown into doubt by the UN-backed election complaints commission ordering a number of recounts and audits of votes.
It warned that it had found "clear and convincing evidence of fraud".
The 20 August election has been overshadowed by claims against all the main candidates of fraud and ballot-box stuffing.
James Robbins, BBC diplomatic correspondent
When the polls closed in Afghanistan almost three weeks ago, political and military leaders in London and Washington breathed a sigh of relief.
Violence had failed to prevent healthy turnouts in most areas.
One hurdle cleared. But the real test set by the international community was the credibility of the results, as well as the process - and that is now in real doubt.
If fraud could actually have swung the result, and that's still unclear, questions over the entire mission in Afghanistan will intensify, particularly because Britain and the US have both suffered record numbers of soldiers killed in recent weeks.
A credible election result was seen as a key objective for the West, as it continues its campaign against the Taliban.
The latest results came in from the south, where President Karzai enjoys strong support.
The Independent Election Commission (IEC) said that Abdullah Abdullah remained second, with 28.3% of the vote.
However, it said it had "quarantined" results from 600 polling stations where it suspects irregularities. The list of those stations has been sent to the complaints commission (ECC).
Mr Abdullah claimed the move vindicated his decision to raise fears of fraud shortly after the election and said announcement of the results should have been delayed in light of these suspicions.
"I think [the] real outcome, after seeing the complaints, will be quite different from what you have seen today," he said.
Announcing the results before the allegations had been investigated broke the rules of the electoral process, he claimed.
Earlier, the ECC said a recount and inspection should be done for any polling station where 600 or more votes were cast, or where any single candidate got more than 95% of votes.
It was the first time the ECC had gone public with accusations of fraud.
Commission chairman Grant Kippen said it was not known how many polling stations this would involve.
He said investigations conducted in Ghazni, Paktika and Kandahar found "clear evidence of irregularity" within polling stations and ballot boxes.
"We decided based on those investigations... that we would order the IEC to conduct an audit and recount of polling stations around the country."
Results from a number of polling stations showed President Karzai winning 100% of the vote.
The BBC's Chris Morris in Kabul says recounts could strip President Karzai of many votes.
Although the likelihood is that President Karzai will emerge the victor, how much legitimacy and credibility that victory has will be another question, our correspondent says.
An IEC official told the BBC that although final provisional results will be announced on Saturday, the recounts could take a long time.
The ECC may also have to investigate and rule on further complaints of irregularities, which could lead to more delays, the official said.
IEC chief electoral officer Daoud Ali Najafi said it could take two to three months to comply with the ECC's audit and recount order.
Analysts say that a second round of voting, if needed, would be difficult to hold beyond the end of October because of Afghanistan's extreme weather.
The election results have been released piecemeal by the IEC.
The previous figures, released on Sunday, gave Mr Karzai 48.6% of the vote against 31.7% for Mr Abdullah.
Last month's election day was marred by more than 400 Taliban attacks, including against voters whom the insurgents had warned not to turn out.
The US is considering whether to send thousands more troops to the country, where violence has hit a record high eight years after the US-led invasion.