More than 16,000 complaints have been filed to Afghan election authorities over the handling of this year's presidential polls, officials said Thursday, days after preliminary results put President Ashraf Ghani in place to secure a second term.

Afghanistan's Independent Election Commission (IEC) announced earlier this week that Ghani had won a slim 50.64 percent majority in the September 28 poll.

The final results are expected to be announced in the coming weeks after the complaints have been reviewed.

"(Officials) have 15 days to finalise its investigation into the complaints and release the results to the candidates," said Zuhra Bayan Shinwari, head of the Independent Electoral Complaints Commission (ECC), adding that 16,500 complaints were received in total.

If the numbers hold following these investigations, the result is enough for Ghani to avoid a run-off, after he easily beat his long time rival Chief Executive Abdullah Abdullah, who scored 39.52 percent.

According to Shinwari, Abdullah's team filed around 8,000 complaints to the ECC and Ghani handed in over 3,000, while the rest were submitted by other candidates.

Preliminary results originally due October 19 were repeatedly delayed for what the IEC said were technical issues. Various candidates, particularly Abdullah, alleged fraud.

The election was meant to be the cleanest yet in Afghanistan's young democracy
The election was meant to be the cleanest yet in Afghanistan's young democracy AFP / FARSHAD USYAN

Observers and candidates have blasted the IEC over its handling of the count and its repeated disregard of the electoral calendar.

The election was meant to be the cleanest yet in Afghanistan's young democracy.

A German firm supplied biometric machines to stop people from voting more than once.

But allegations of vote stuffing, illegal balloting and other fraud came almost as soon as the polls had closed.

Nearly one million of the initial 2.7 million votes were purged owing to irregularities, meaning the election saw by far the lowest turnout of any Afghan poll.

Ultimately, only 1.8 million votes were counted -- a tiny number given Afghanistan's estimated population of 37 million and a total of 9.6 million registered voters.

Abdullah lost to Ghani in 2014 in a divisive election that saw the US intervene to broker an awkward power-sharing deal between the two rivals.