By Jeremy Laurence
KABUL, April 20 (Reuters) - Former foreign minister Abdullah Abdullah has opened a lead in the Afghan presidential race, the latest official tally of votes released on Sunday showed, although half of the votes have yet to be counted.
Afghanistan's Independent Election Commission said initial results based on almost 50 percent of the vote out of 34 provinces showed Abdullah in the lead with 44.4 percent, followed by ex-world bank official Ashraf Ghani with 33.2 percent of the votes it said were not fraudulent.
"These statistics that we shared with you are partial and are changeable," Ahmad Yusuf Nuristani, chairman of the election commission, told a news conference on Sunday.
To win, a candidate must secure more than 50 percent of valid ballots. Failing that, the top two candidates go into a run-off. Final results are due on May 14, and a run-off, if needed will take place in late May.
A run-off is seen as a risky proposition in Afghanistan, given high security concerns, the prospect of a low turnout and the cost - the bill for the first round was put at more than $100 million.
Afghanistan's allies hailed the first round on April 5 a success because of the high number of participants and the fact that Taliban militants didn't stage any big attacks on polling day.
All leave for hundreds of thousands of police and soldiers was cancelled as the government made security a top priority.
Official estimates put the turnout at 60 percent of 12 million eligible voters. But there as many as 18 million voter cards are in circulation.
Evidence of widespread fraud has taken some of the gloss off the third presidential election since U.S.-led forces drove the Taliban from power in 2001.
Over a million votes are likely to be thrown out, and election officials have also warned that the high incidence of fraud could delay the entire election process.
"High ranking officials all the way from governors to MPs were involved in ballot stuffing," Gul Agha Sherzai, one of the nine candidates and former governor of Kandahar, told Reuters. "District commanders, police officials, everybody was involved - the previous election, nothing like this happened."
More incidents of serious fraud were reported in this month's vote than in the previous ballot of 2009, threatening to undermine the legitimacy of an election meant to usher in Afghanistan's first democratic transfer of power.
A YEAR OF TRANSITION
Hamid Karzai was constitutionally bound to step down as president after more than 12 years in power, at a time when Afghanistan prepares to stand on its own feet as most Western troops prepare to leave the country by the end of the year.
Western powers are watching the process intently after a messy presidential election in 2009 resulted in allegations of mass fraud and ballot stuffing.
Foreign donors, who are hesitant about bankrolling the Afghan government after the bulk of NATO troops leaves, will also closely scrutinise the composition of the country's future government to decide if they can work with the new team.
Abdullah, a trained ophthalmologist turned anti-Soviet resistance fighter, quit the last election after complaining the poll was marred by massive ballot box stuffing. He had been due to contest a second round run-off against Karzai.
The former foreign minister has said he had already discussed joining forces with other candidates for a run-off, including Rassoul, who is backed by two of Karzai's brothers. (Additional Reporting by Mirwais Harooni and Hamid Shalizi; Writing by Jeremy Laurence)