Citing irregularities, the Supreme Court said a new poll should be held within 60 days.
Kenya’s Supreme Court has nullified the result of the August 8 presidential election won by President Uhuru Kenyatta.
In a ruling issued on Friday, the court said the electoral board committed “irregularities and illegalities” during last month’s vote, harming the integrity of the election.
The court ordered another presidential election to be held within 60 days.
“The declaration [of Kenyatta’s win] is invalid, null and void,” said Judge David Maraga, announcing the verdict of four out of the six judges.
No Kenya presidential election has ever been nullified.
Maraga saying the election commission “failed, neglected or refused to conduct the presidential election in a manner consistent with the dictates of the constitution”.
The protest was brought before the Supreme Court by opposition leader Raila Odinga, who lost to Kenyatta.
Kenyatta was announced the winner with 54 percent of the vote – but Odinga claimed the election was rigged with electronic voting results hacked into and manipulated in favour of Kenyatta.
Kenya’s electoral commission had said there was a hacking attempt but it failed. International election observers said they saw no interference with the vote.
Odinga supporters erupted in jubilation after the decision was announced.
“This is an unprecedented ruling,” Odinga said outside the court. “This is a triumph for the people of Kenya.”
Odinga’s lawyer had asked the court to invalidate Kenyatta’s win, saying a scrutiny of the forms used to tally the votes had anomalies that affected nearly five million votes.
Al Jazeera’s Mohamad Adow, reporting from Nairobi, said the ruling was “historic, unprecedented anywhere in Africa”.
“What has happened here today is huge on any scale,” he said.
Unease around the election rose when the official who oversaw the electronic voting system was found tortured and killed days before the vote.
Unrest following the vote was far calmer than the post-election violence a decade ago that left more than 1,000 people dead.