"These results are fake, it is a sham. They cannot be credible," Odinga told a press conference in the early hours of the morning as partial results fell quickly via an electronic tallying system aimed at preventing fraud.

Results released by the electoral commission (IEBC) showed Kenyatta leading with 55% of the nearly 13 million ballots counted against Odinga's 44%, a difference of nearly 1.4 million votes.

Odinga claimed the IEBC had not provided documents that would show how the tallies were arrived at.

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"It is the machine that has voted," Odinga told reporters. "These results are wrong."

Odinga, 72, who is making his fourth stab at the presidency, accused his rivals of stealing victory from him through rigging both in 2007 and 2013.

In 2007, the disputed vote resulted in two months of ethnically-driven political violence that killed 1,100 people and displaced 600,000 in a major blow to a nation seen as a regional bastion of stability.