"The court finds the applicant has failed to place before it clear, direct, sufficient and credible evidence" of irregularities, Malaba said in his ruling at the Constitutional Court in Harare.

"There was no proof of the happenings of these irregularities as a matter of fact."

Mnangagwa, of the ruling ZANU-PF party, won the July 30 election with 50.8 percent of the vote - just enough to meet the 50 percent threshold needed to avoid a run-off against MDC leader Nelson Chamisa, who scored 44.3 percent.

His inauguration would now take place on Sunday, justice minister Ziyambi Ziyambi told AFP.

Lawyers for the Movement for Democratic Change (MDC) had argued that the results should be annulled due to alleged "massive doctoring" of the vote.