Kenya opposition presidential candidate Raila Odinga has said the electoral commission’s IT system has been hacked to manipulate the election results.
He rejected early results indicating a strong lead for his rival, President Uhuru Kenyatta.
Mr Odinga earlier told journalists the details were “fake”, because the authorities had failed to present documents verifying the results.
Many fear a repeat of the violence after a disputed election 10 years ago.
More than 1,100 Kenyans died and 600,000 were displaced following the 2007 vote.
Electoral officials say that with 91% of results in, Mr Kenyatta is leading with about 54.5%, to Mr Odinga’s 44.6%.
Mr Kenyatta’s lead could mean that he is elected outright. There were eight candidates in all, but apart from Mr Kenyatta and Mr Odinga none polled more than 0.3% of the vote.