NAIROBI (Reuters) - Kenyan presidential candidate Uhuru Kenyatta's share of the vote slipped below 50 percent for the first time in the slow counting of results on Thursday, raising the prospect that the country could be headed for a divisive second round run-off.
Kenyatta's main rival, Prime Minister Raila Odinga, narrowed the gap to within three percentage points as votes from his stronghold were added to the tally.
Earlier on Thursday, Odinga's campaign team said some of the results of the election had been doctored and called for the vote count to be halted, remarks that could inflame public passions after a previously largely peaceful poll.
Kenyans have been anxiously awaiting the result since Monday, fearful of a repeat of a disputed outcome in the last election five years ago, which led to ethnic bloodshed that killed 1,200 people.
Kalonzo Musyoka, Odinga's running mate, said his party's challenge to the vote count was not a call for mass action and urged voters to stay calm and patient.
Kenyatta, son of Kenya's independence leader Jomo Kenyatta, has been indicted for crimes against humanity over the ethnic violence that followed the last election, posing a dilemma for Western allies if he wins.
He has been leading since the first tallies were tabulated earlier in the week, but his share of the vote has slipped from over 50 percent to just below it. If neither candidate wins more than half of votes, Kenyatta and Odinga must face each other in a run-off, pencilled in for next month.
By 2035 GMT, with 7.23 million total votes tallied, Kenyatta had 3,522,127 or 48.7 percent, to Odinga's 3,299,391 or 46.07, according to a display by the electoral commission at the national tallying centre.
About a quarter of votes had yet to be counted, representing 128 of 291 constituencies.
Despite technical glitches, international observers have in past days broadly said the vote and the count were transparent. But Odinga's running mate Musyoka, speaking earlier in the day when the tally still showed Kenyatta on course to win in a single round, said counting should be stopped.
"We as a coalition take the position the national vote tallying process lacks integrity and has to be stopped and re-started using primary documents from the polling stations," he told a news conference. "We have evidence the results we are receiving have been doctored."
Election officials said the count would not stop and the results could be delivered by Friday. The commission has up to seven days from Monday's vote to declare the outcome.
"The commission wishes to assure Kenyans that with the rigorous verification process in place, there is no room to doctor the results whatsoever by any election official," said Issack Hassan, chairman of the Independent Electoral and Boundaries Commission.
"We cannot stop tallying, this is a legal process..."
Kenyans have been hoping this vote would restore the country's status as one of Africa's most stable democracies after the electoral mayhem five years ago. Many have voiced determination not to take their differences to the streets but to turn to a reformed judiciary to resolve any new disputes.
Witnesses said areas in the capital Nairobi and Kisumu, a city in the west of Kenya where violence erupted after the 2007 vote, appeared calm shortly after Musyoka's comments.
"It is not a call to mass action," Musyoka said. "We must tell them (Kenyans) there will be no mass action. We are committed as a coalition to the principle of the rule of law."
The Kenyan shilling has been volatile against the U.S. dollar with each twist and turn of election, climbing when a clear result looked like it could emerge swiftly but weakening with the uncertainty of the slow count.
Kenyatta's coalition has also complained about the inclusion of rejected ballots in the vote count, although it has not called for a halt in counting. Both teams have also urged voters to be patient.
Kenyatta and his running mate, William Ruto, have both been charged by the International Criminal Court (ICC) in The Hague for orchestrating the tribal blood-letting after the 2007 vote. They both deny the charges and say they will cooperate to clear their names, regardless of the election outcome.
Judges at the ICC agreed on Thursday to delay the start of Kenyatta's trial for crimes against humanity to July 9 from April 11, to give defence lawyers more time to prepare. That, at least, means the trial would not directly interfere with a potential second round of voting in April.
Musyoka questioned the sharp fall in the number of spoilt ballots counted as Kenya scrapped an electronic tallying system and switched to rely solely on a manual one. The amount of spoilt ballots could have a significant impact on the outcome, especially if the final tally remains close.
The election commission chairman Hassan said the original high figure for spoilt ballots was due to a computer error.
Authorities were forced to abandon an electronic counting system which had aimed to provide speedy provisional results but broke down. That has given time for both camps to complain over the process.
Voting passed off broadly peacefully, and Kenyans have said they are determined to see it stay that way. Many businesses have stayed closed or kept stocks low as a precaution against the violence and looting that erupted last time.
The government on Thursday ordered all civil servants to report to work on Friday, after four days in which many had stayed away from their offices.
In Nairobi's Mathare slum, a flashpoint in the violence five years ago, residents played down any talk of bloodshed.
"I don't anticipate any violence. We are all Kenyans and there is no need to fight. We voted peacefully, let's maintain that peace," said Shadrack Otieno, a 37-year-old Odinga backer.
In Kisumu, the biggest city in Odinga's tribal heartland, businesses which had shut for voting started re-opening for the first time in four days. But some people suggested the quiet might not last.
"If this trend continues then we will protest in the streets," minibus taxi conductor Joseph Omwaru told Reuters, adding he believed there was rigging in Kenyatta's favour.
Additional reporting by Richard Lough, Duncan Miriri and Yara Bayoumy in Nairobi, Drazen Jorgic in Mombasa and Hezron Ochiel in Kisumu; Writing by James Macharia and Edmund Blair; Editing by Peter Graff