Veteran opposition leader Raila Odinga is leading Kenya's presidential race, official election results show, pushing Deputy President William Ruto into second place.
With just more than 26 per cent of votes counted, Odinga had 54 per cent and Ruto had 45 per cent, according to results provided on Saturday by the Kenyan election commission and displayed on a large screen at a national tallying centre in the capital, Nairobi.
East Africa's wealthiest nation and most vibrant democracy held presidential, parliamentary and local elections on Tuesday.
Ruto and Odinga are in a tight race to succeed President Uhuru Kenyatta, who has reached his two-term limit. Kenyatta fell out with Ruto after the last election and has endorsed Odinga.
Official vote tallying has been proceeding slowly, fuelling public anxiety.
Election commission chairman Wafula Chebukati blamed party agents, who are allowed to scrutinise results forms before they are added to the final tally.
"Agents in this exercise cannot proceed ... as if we are doing a forensic audit," he told a news briefing on Friday.
"We are not moving as fast as we should. This exercise needs to be concluded as soon as possible."
Reuters and other media outlets have been tallying results forms from 291 constituencies posted on the election commission website. These have not yet been verified, and this tally is running well ahead of the official one.
As of 1000 GMT (2000 AEST), Reuters had tallied 236 forms, which showed Ruto in the lead with nearly 53 per cent of the vote, compared with just more than 46 per cent for Odinga.
Two other candidates had less than one per cent between them.
Nineteen other forms could not be included in the count because they were unreadable or were missing information.
After the forms are uploaded to the commission's website, they must be physically brought to the national tallying centre, where party representatives can examine them for discrepancies.
The process was designed as a safeguard against the kind of rigging allegations that have triggered violence after previous polls. More than 1200 people were killed after a disputed 2007 election and more than 100 killed after a disputed 2017 election.
The winning candidate must receive 50 per cent of the national vote plus one, and at least 25 per cent of the vote from 24 of 47 counties.
The commission has until Tuesday to declare a winner.
Australian Associated Press
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