National Super Alliance (Nasa) presidential candidate Raila Odinga says they are moving to the Supreme Court to contest President Uhuru Kenyatta win in August 8 poll.
Mr Odinga on Wednesday termed as "computer-generated", Mr Kenyatta's victory as declared by the Independent Electoral and Boundaries Commission (IEBC).
He said their decision to fight Mr Kenyatta in court was partly informed by the ongoing crackdown on pro-democracy civil societies, including the Africa Centre for Open Governance and Kenya Human Rights Commission.
Their mission in the top court in the land, Mr Odinga said, is to "demonstrate to the whole world the making of a computer-generated president".
"We will show the world how the figures were cooked and Uhuru Kenyatta declared the winner," Mr Odinga said at Okoa Kenya offices in the capital Nairobi.
"Kenyans will not agree to be led by computer-generated leaders."
Results streamed by the IEBC, he said, were not backed by forms 34B, the documents signed by party and candidates' agents in constituencies.
He particularly queried Mr Kenyatta's 11 percent "consistent lead" in the results posted on IEBC web portal, terming it "the work of a computer algorithm".
"Yesterday (Tuesday) Chiloba admitted that all forms 34B were not in and, therefore, results were null and void," he said, referring to IEBC CEO Ezra Chiloba.
"Uhuru wasn't supposed to be declared as the winner."
His comment came hours after the commission, in a Twitter post, said forms 34B for all constituencies were available to the public to scrutinise the results.