A candidate needs more than 50% of votes to avoid a run-off.
The BBC's Ian Pannell in Kabul says this is still a small fraction of the overall count and it will take some time for a fuller picture to emerge.
Analysts say any preliminary claims about the result must be viewed with caution in the light of the allegations of fraud, corruption and ballot-stuffing and concerns about low voter turnout, especially in the south.
The official adjudicators, the Electoral Complaints Commission (ECC), are investigating more than 1,000 complaints of fraud and irregularities and, out of these, at least 50 are considered to be very serious.
Our correspondent says there are also fears that supporters of the losing candidates could take to the streets if they feel that the election has not been legitimate.
The international community is urging patience and calm until all complaints have been investigated and the final results are announced.
Some feel Afghan and Western officials were too swift to declare last Thursday's poll a success, despite concerns about the turnout, especially in the insurgency-wracked south.
The Nato-led International Security Assistance Force (Isaf) said there were more than 400 insurgent attacks on election day, which would make it one of the most violent days in Afghanistan since 2001.
The UK ambassador in Kabul, Mark Sedwill, has defended the use of the international force to provide security for the elections.
He was responding to unconfirmed reports that in one area secured during Operation Panther's Claw in Helmand Province, just 150 voted.
Ten British soldiers died during the mission to drive the Taliban out of Babaji district and the surrounding area.
Just hours after the first results on Tuesday, a huge bombing in the southern city of Kandahar left more than 40 people dead.
It came on the same day four US soldiers were killed, making 2009 the deadliest year for foreign troops in Afghanistan since the US-led overthrow of the Taliban in 2001.
On Wednesday, a bomb attack in Kunduz in the north-east killed the head of the province's justice department, Qari Jahangir, police said.
The Taliban said they killed Mr Jahangir but have denied carrying out the Kandahar attack.
Correspondents say the militants often deny responsibility for attacks in which civilians are killed.
Did you vote in the Afghan elections? What are your voting experiences? Send us your comments using the form below.
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.