An election worker carries a ballot box at an election commission office in Jalalabad, Nangarhar province, east of Kabul on Tuesday. (Rahmat Gul/Associated Press)

Early results from the Afghanistan election show incumbent President Hamid Karzai has a slight lead with 41 per cent of the vote after 10 per cent of the polls have reported, the Electoral Commission said Tuesday.

Abdullah Abdullah, the former foreign minister and top challenger, has 39 per cent of the vote.

The commission plans to release partial results each day for the next several days. Final results won't be made public until mid-September or late in the month.

Tuesday's results were based on 524,000 valid votes counted after 31,000 votes were thrown out, the commission said.

Less than two per cent of Kandahar votes have been counted, and no votes in Helmand have been tallied, the commission said. Karzai is expected to do well in both provinces, so his returns could go higher.

Karzai needs a simple majority of more than 50 per cent to avoid a second round run-off.

The partial results come after low voter turnout and amid allegations of fraud and fears of post-election violence.

Possible 'increased tension and violence'

Meanwhile, six Afghan presidential candidates warned in a statement that "fraud in last Thursday's elections could result in increased tension and violence."

They said "their questions must be answered" by the elections commission and international observers.

The were all long-shot candidates, the most prominent being Ashraf Ghani, a Western-educated former finance minister being touted as the "chief executive" under the next president.

On Monday, the country's finance minister claimed at a private dinner that Karzai has won with close to 70 per cent of the vote.

The campaign team for Abdullah dismissed that statement, saying their candidate is in the lead.

There are worries that Abdullah's supporters could vent fury if he comes in second with no chance at a run-off, which would be triggered if no candidate wins more than 50 per cent of the vote.

A presidential spokesman said the government was prepared to respond to any post-election unrest.

As of Monday evening, the independent Electoral Complaints Commission said it had received more than 50 allegations of fraud that could affect the election results if true.

Final results cannot be certified as legitimate until the complaints commission rules on these cases.

With files from The Associated Press