By Yara Bayoumy and Duncan Miriri

NAIROBI (Reuters) - Kenyan authorities were racing to gather final election results on Wednesday, with the partial count still giving the lead to a politician who faces charges in The Hague for ethnic killings following the 2007 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 the rival camp of Prime Minister Raila Odinga, 68, say some of their strongholds have yet to declare their results.

About 1,200 people were killed in weeks of tribal violence after the 2007 election, when 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 the large-scale unrest.

But many Kenyans are worried by the delays.

"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. "It makes us nervous, and it's just adding to the tension."

A dispute over a sizable number of rejected ballots could rein in Kenyatta's early lead and raise the chances of an April run-off, prolonging the uncertainty.

The Independent Electoral and Boundaries Commission (IEBC) was manually tallying results from returning officers after the electronic system to transmit provisional figures failed. It has seven days from the vote to declare the official outcome.

Albert Bwire, a commissioner at the electoral authority said he hoped the final tally could be completed "preferably by the end of day tomorrow (Thursday)".

Despite technical glitches, European Union chief observer Alojz Peterle said the vote was credible and transparent so far.

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.

WAIT TAKES TOLL

Kenyatta and his running mate, William Ruto, both face trial at the International Criminal Court on charges of unleashing death squads after the 2007 election. Both men deny the charges and have said they would cooperate with the court and go to The Hague to clear their names.

Worries about the outcome are taking their toll. Many shops and businesses have run down stocks for fear of a repeat of the looting after the previous election, which has pushed up food prices in some places.

"Life is becoming difficult and unbearable here," said Milka Achieng, 42, a mother of five in 2007 flashpoint Kisumu, who now has to pay three times the normal price for cabbages. "I plead with the IEBC to quickly announce the results so that life can continue."

Investors initially applauded the peaceful voting and the early signs of a clear winner by pushing the shilling to its strongest level against the dollar in 18 weeks on Tuesday, but weakened 1 percent against the dollar on Wednesday due to concerns that delays in the announcement of presidential election results would prompt rivals to challenge the outcome.

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, on 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, that would sharply erode Kenyatta's chances of securing the more than 50 percent needed in the first round for an outright win.

"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."

RESTORING IMAGE

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."

British High Commissioner Christian Turner was singled out for criticism by the Jubilee coalition for seeking to meddle in the vote. In a statement, Turner dismissed such accusations as "entirely false and misleading".

Odinga's camp has 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. The vote commission said it was deploying helicopters to ferry returning officers from far-flung areas.

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.

Kenya is East Africa's biggest economy and, though led by authoritarian leaders accused of corruption for most of its half century of independence, has been spared the civil wars that devastated neighbors 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 neighborhood in Nairobi late on Tuesday, injuring one person.

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 that 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. But the rising concerns are barely concealed.

"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."

(Additional reporting by Kevin Mwanza and George Obulutsa in Nairobi, Hezron Ochiel in Kisumu and Drazen Jorgic in Mombasa; Writing by Edmund Blair and James Macharia)