Kenya opposition presidential candidate Raila Odinga has said the electoral commission’s IT system has been hacked to manipulate the election results.
He rejected provisional results from Tuesday’s vote indicating a strong lead for President Uhuru Kenyatta.
Kenya’s election chief Wafula Chebukati said he had confidence in the system but the claims would be investigated.
Many fear a repeat of the violence after a disputed election 10 years ago, and there have been calls for calm.
More than 1,100 Kenyans died and 600,000 were displaced following the 2007 vote.