The IECB said it hoped to release final results from the presidential poll on Friday.
According to the opposition brigade, their parallel tallying shows Raila leading the race, beating Uhuru with hundreds of thousands of votes as opposed to IEBC's tally that shows Raila trailing Uhuru by about 1.5 million votes.
Observers drawn from the African continent have described the 2017 Kenya election process as a free and fair poll, a statement which they say is highly attributed to the well preparedness of the Independent Electoral and Boundaries Commission (IEBC).
The opposition leader's comments have raised fears that his supporters could mount street protests.
Millions of Kenyans went to the polling stations on Tuesday in the third presidential elections since the 2007 elections when rage over former President Mwai Kibaki's disputed re-election killed more than 1,200 people, injured 3,500 and forcibly displaced up to 650,000 others. But he added: "I don't control the people".
Another top Western observer, speaking on the condition of anonymity because observers do not want to be seen as interfering, cast doubt on Mr. Odinga's assertions.
But there were clashes in his hometown of Kisumu, with police firing tear gas at protesters.
Odinga said: "We fear this was exactly the reason Chris Msando was assassinated, so this could happen". We encourage members of public to start tracking the results.
They later used live rounds to disperse another group, while a pro-Odinga protester was shot dead by police in a Nairobi slum, witnesses said.
Nasa spokesman Musalia Mudavadi said that the coalition would submit its evidence of fraud to the election board - but appealed for Kenyans to remain "calm".
"We find ourselves at a crossroads once again", the Daily Nation newspaper warned grimly.
"Hacking was attempted but did not succeed, that is our position", said Chebukati.
Foreign observers praised a peaceful, credible voting process, but the mood quickly turned sour when Odinga rejected the results after only a few hours of counting.
Former U.S. secretary of state John Kerry is part of the worldwide election observation mission.
Odinga, 72, who claimed elections in 2007 and 2013 were stolen from him, charged that hackers broke into the election commission's systems and rigged the count - an allegation that fuelled uncertainty in what was already a tight race.
Nauert lauded the millions of Kenyans who on Tuesday peacefully exercised their fundamental democratic right to choose their leaders.
"It is a sign of leadership and public service to be able to congratulate your opponent with grace as a normal and important part of democracy", Marietje Schaake, head of the European Union mission, said in a statement Friday. "Despite the anxiety, they don't have time to reflect".