* New electronic system plagued by hitches, slows count
* More than 1,200 were killed after a disputed 2007 poll
* Kenyatta coalition unhappy about use of void votes
* Questions over whether candidates will accept result
Kenyan authorities were racing to gather final election results on Wednesday after a partial count gave the lead to a politician wanted in The Hague over violence following the previous vote.
Counting since Monday's voting has been slow and complicated by hitches in a new electronic system. Politicians have complained about flaws in the process, stirring fears of a repeat of the troubles after the election five years ago.
Deputy Prime Minister Uhuru Kenyatta, 51, has kept an early lead since poll results started trickling in but some strongholds for his rival Prime Minister Raila Odinga, 68, have yet to declare their results.
The last election saw some 1,200 people killed in ethnic violence after outgoing president Mwai Kibaki was declared the victor over Odinga amid charges of voting fraud.
Kenyans are waiting to see if politicians will respect the vote results this time. At least 15 people were killed in pockets of violence as voting took place on Monday but so far there has been no repeat of large scale unrest.
A dispute over a sizable number of rejected ballots could rein in Kenyatta's early lead and raise the chances of an April runoff, prolonging the uncertainty.
"We are afraid because we don't know what's going to happen next," said Charles Kabibi, 27, a gardener in the port city of Mombasa, whose concerns have risen with the wait. "It makes us nervous and it's just adding to the tension."
The election commission has said it aims to start tallying final results from returning officers on Wednesday after the electronic system to transmit provisional figures failed. But it has seven days from the vote to declare the official outcome.
Alojz Peterle, chief observer of the European Union mission, said the process had been credible and transparent so far.
Kenyatta and his running mate, William Ruto, are both wanted in The Hague on charges of unleashing death squads after the last vote in 2007. Both men deny the charges.
The United States and other Western states, big donors that view Kenya as vital in the regional battle with militant Islam, have already indicated that a victory by Kenyatta would complicate diplomatic relations.
CALL FOR CALM
Provisional results displayed by the election commission on Wednesday with about 60 percent of polling stations still to report showed Kenyatta, son of Kenya's independence leader and one of Africa's richest men, leading with 53 percent, against 42 percent for veteran politician Odinga.
But the numbers ignore more than 330,000 rejected votes that have been counted so far. The election commission says they will now be included in a final calculation. Once factored in, Kenyatta's chances of securing more than 50 percent in the first round to give him an outright win would be sharply eroded.
"We want to believe that this is not an attempt to deny the Jubilee Coalition a first-round victory as is clearly now on the wall," Ruto told reporters, referring to a results screen. "We urge every Kenyan to be calm and very patient and await the official release of these results by the commission."
He also suggested foreigners might have prompted the commission's change of heart, adding: "We are very concerned at the level of involvement of ambassadors and foreigners in canvassing for various positions around this hall."
Odinga's camp has also questioned parts of the election process before, during and after the vote, hinting at the potential for legal challenges.
Franklin Bett of Odinga's CORD coalition said the commission would struggle to give a final result on Wednesday. "It's not possible," he said, adding that the commission was using helicopters to ferry returning officers from far flung areas.
The electoral commission said it was relying on manual delivery of results after the new technology that aimed to help prevent a repeat of the violence after the December 2007 vote by offering greater speed and transparency fell short.
"What matters here is the final result and they are coming in," election commission Chairman Ahmed Issack Hassan said late on Tuesday, calling for patience from voters and candidates.
Kenyans, who often had to queue for hours to vote, hope the vote will restore the nation's image as one of Africa's more stable democracies, damaged by the tribal blood-letting in 2007.
Election officials said turnout was more than 70 percent of the 14.3 million eligible voters.
Kenya is East Africa's biggest economy and, although led by authoritarian leaders accused of corruption for most of its half century of independence, has been spared the civil wars that devastated neighbours like Somalia, Sudan, Uganda and Rwanda.
It won support from the West for sending troops to Somalia to fight al-Shabaab Islamist militants. Highlighting the threat, an explosion struck a predominantly Somali neighbourhood in Nairobi late on Tuesday, injuring one person.
Investors on Tuesday initially applauded the peaceful voting and early signs of a clear winner by pushing the shilling to its strongest level against the dollar in 18 weeks. But the delay in results has weighed on nerves and the currency has given up its gains.
As in past elections in Kenya, much of the voting has been on ethnic lines, with Kenyatta enjoying strong support among his Kikuyu tribe, Kenya's largest, and Odinga backed by the Luo, the tribe which includes the family of U.S. President Barack Obama.
In a country with a handful of large tribes and dozens of smaller ones, both candidates lead broader coalitions and are also relying on support from the tribes of their running mates.
All the candidates have pledged to accept the outcome, and ordinary Kenyans speak passionately about their determination not to allow a repeat of the violence five years ago.
Streets have been all but deserted with many businesses closed, including supermarkets and security personnel were beefed up countrywide in readiness for possible demonstrators.
"We are worried about violence and the businesses are not doing well," said Francis Mwangi, 25, a technician in Mombasa. "People are not working because they're waiting for results so they can start once more.