International observers on Thursday praised the handling of Kenya's presidential election, with the European Union mission saying it had seen no sign of manipulation despite opposition complaints and scattered protests.
Police fired live rounds and tear gas as they clashed with opposition supporters in one Nairobi neighbourhood but most of the capital and the rest of the country were calm after four people were killed in violence on Wednesday.
President Uhuru Kenyatta has taken a commanding lead but his rival, veteran opposition leader Raila Odinga, has rejected provisional electronic results, saying figures released so far are "fictitious" and that election systems had been hacked.
Kenya's election commission suffered a hacking attempt after this week's vote but the system was not compromised, its chairman said on Thursday.
"Hacking was attempted but did not succeed," commission chairman Wafula Chebukati told a news conference. He did not elaborate.
As they wait for final results to be tallied and confirmed, many Kenyans are nervous of a repeat of the clashes that killed about 1,200 people after a bitterly contested 2007 election.
In its first assessment of Tuesday's poll, the European Union's election observer mission said it had seen no signs of "centralised or localised manipulation" of the voting process.
Marietje Schaake, head of the mission, said the EU would provide an analysis of the tallying process in a later report.
Provisional results released by the election commission showed Kenyatta had won 54.3 percent of votes, ahead of Odinga on 44.8 percent – a lead of 1.4 million votes with 97 percent of polling stations reported.
John Kerry, the former US secretary of state heading the Carter Center observer mission, said the election system, which is ultimately based on the original paper ballots cast, remained solid and all sides should wait for electronic tallies to be double-checked against hard copies.
"The process that was put in place is proving its value thus far," Kerry said. "Kenya has made a remarkable statement to Africa and the world about its democracy and the character of that democracy. Don't let anybody besmirch that."
Election results to come Friday
Kenya's electoral commission said on Thursday it only expects all presidential results to arrive at the national tallying centre by midday on Friday for validation, and called for "restraint" from political parties.
Tensions are high after opposition candidate Raila Odinga rejected partial results and alleged there had been a massive hacking attack on the electronic vote-tallying system.
Electoral commission (IEBC) chairman Wafula Chebukati said: "Hacking was attempted but did not succeed, that is our position."
Odinga's claims, as he fell behind incumbent Uhuru Kenyatta in provisional results, sparked angry protests on Wednesday in which two protesters were shot dead by police. Another two people were shot dead by police for allegedly attacking a polling station.
"We ask all parties to continue to exercise restraint especially at this critical moment," said Chebukati.
"We are working hard to ensure that we get the final results within the shortest time possible. We expect that all the presidential results ... will reach the national tallying centre by 12:00 pm tomorrow (Friday)."
He said the results would be validated and that a final decision would be announced "soon thereafter."
Kenya's election commission said that it hoped to have all results centralised by midday on Friday and would announce a winner soon after that. It confirmed there had been an attempt to hack into its system but said it had failed.
Thabo Mbeki, the former South African president in charge of the African Union observer mission, praised the poll so far.
"It would be very regrettable if anything emerges afterwards that sought to corrupt the outcome, to spoil that outcome," he said.
"I don't control the people"
Kenyatta, a 55-year-old businessman seeking a second five-year term, held a lead of about 10 percent from the start of Tuesday's counting, the culmination of a hard-fought contest between the heads of Kenya's two political dynasties.
Odinga contested and lost Kenya's last two elections, which he also said were rigged. He has urged his supporters to remain calm but said: "I don't control the people."
He posted 50 pages of computer logs online to support his hacking claims, but they were inconclusive, according to Matt Bernhard, who studies computer security in election systems at the University of Michigan.
In 2007, tallying was halted and the incumbent president declared the winner, triggering an outcry from Odinga's camp and waves of ethnic violence that led to International Criminal Court charges against Kenyatta and his now-deputy, William Ruto.
The cases against them collapsed as witnesses died or disappeared.