Afghanistan's presidential election result was delayed on Wednesday as authorities said they had not completed fraud investigations into the first round of voting to find a successor to Hamid Karzai.

Full results from the April 5 election were released late last month, but the final declaration will factor in the outcome of weeks of deliberation over fraud allegations.

Afghan election front-runner Abdullah Abdullah received a major boost to his presidential campaign on Sunday with the endorsement of third-placed Zalmai Rassoul, a close ally of the current leader.

Rassoul was seen as the favored candidate of outgoing President Hamid Karzai, and his support for Abdullah could be influential in deal-making to choose Afghanistan's next leader as US-led troops withdraw from the country.

President Barack Obama offered his Afghan counterpart Hamid Karzai additional U.S. assistance Sunday to relief efforts after a landslide killed hundreds of people in northern Afghanistan.

Much of Aab Bareek village in Badakhshan province was swallowed on Friday by a fast-moving tide of mud and rock that swept down the hillside and left almost no trace of hundreds of homes. 

Afghan presidential candidate Ashraf Ghani pledged Sunday to fight on after coming second in preliminary election results, setting the stage for a difficult run-off vote likely to be targeted by Taliban militants.

Another expensive, and potentially violent, election could be avoided by negotiations between the two leading candidates in the coming weeks, but both sides have dismissed talks of a possible power-sharing deal.

Afghanistan's presidential election result has been delayed by two days due to fraud investigations and will now be released on Saturday, officials said Wednesday as they vowed to sift out fake votes.

Partial results from the April 5 election to succeed President Hamid Karzai have already been released, with former foreign minister Abdullah Abdullah ahead of his main rival Ashraf Ghani after half of the ballots were counted.

Former foreign minister Abdullah Abdullah is well ahead of his main rival in Afghanistan's presidential election, officials said Sunday after half of the ballots were counted, though a run-off vote still looks likely next month.

The Independent Election Commission (IEC) announced that Abdullah was in the lead with 44.4 percent followed by former World Bank economist Ashraf Ghani with 33.2 percent of the votes counted so far from the April 5 election.

U.N. Secretary-General Ban Ki-moon congratulated Afghans on Sunday for the "momentous achievement" of their recent elections, calling for fairness and transparency as the lengthy counting process gets underway.

Afghans braved the threat of Taliban attacks to vote in Saturday's polls to elect a successor to President Hamid Karzai, the first democratic transition of power in the country.

Leading candidates in Afghanistan's presidential election voiced concern Sunday that voting was tainted by fraud, a day after millions defied Taliban threats and turned out to choose a successor to President Hamid Karzai.

World leaders praised the courage of Afghan voters, who cast their ballots in force despite bad weather and the violent campaign of intimidation, and urged patience in the long vote count.

The International Rescue Committee urged the world Wednesday to redouble efforts in Afghanistan, demanding an urgent aid commitment to reverse deteriorating social and economic trends as violence escalates.

The appeal comes three days before Afghans elect a successor to President Hamid Karzai, as NATO combat troops withdraw and the international community slashes aid.

Taliban gunmen abducted a provincial election candidate in northern Afghanistan, officials said on Monday, five days ahead of national polls the Islamist militants have vowed to target.

Afghanistan will vote on Saturday to choose a successor to President Hamid Karzai and to decide the make-up of 34 provincial councils in elections seen as a benchmark of progress since the Taliban were ousted from power in 2001.