Kenya's Supreme Court has ordered fresh elections be held within 60 days after it found the electoral board committed irregularities during the initial round.
Kenya's electoral commission says it will change personnel and processes to prepare for a new presidential vote after the Supreme Court nullified President Uhuru Kenyatta's re-election. Odinga and his supporters argued the August 8 election was hacked to guarantee victory for Kenyatta, who had won a second term with 54 percent of the vote, raking in about 1.4 million more votes than his challenger.
It is the first time in Kenya's history a presidential election result has been cancelled.
Joyous celebrations erupted outside the court and in opposition strongholds after the second term victory of President Uhuru Kenyatta was declared "invalid, null and void".
The legal ruling paves the way for a new race for the presidency between Kenyatta and Odinga. In that judgement there are certain things they will give us about errors what happened during the last election.
The six-judge bench ruled 4-2 in favor of the petition filed by opposition candidate Raila Odinga.
After the election, global monitors from the EU, the African Union and the U.S. had said there was no major fraud on polling day and urged Mr Odinga to concede.
"We are not at war with our brothers and sisters in the opposition because we are all Kenyans", Kenyatta said on national television.
Lawyer for the president, Ahmednasir Abdullahi, condemned it as "a very political decision" but said they would abide by the results. That fear alone will be sure to make people line up in 60 days.
Kenya is the first African country to have a presidential poll invalidated by a court.
Mr. Kerry, heading the Carter Center's observer mission, said, "Kenya has made a remarkable statement to Africa and the world about its democracy and the character of that democracy". Kenyatta won, receiving about 1 million more votes than his opponent.
In Chuka Town, Tharaka-Nithi County, it was business as usual following the news of the Supreme Court decision.
Kenya has a long history of disputed votes, election violence and a lack of faith in the judiciary's independence. "We respect it. We don't agree with it", he said, calling for peace.
Global observers had said they saw no sign of manipulation of voting and tallying at polling stations.
"They are going to have to wipe a huge amount of egg off their faces", John Githongo, an anti-corruption campaigner and former head of Kenya's anti-corruption commission, said of the global observer missions.
Kenya's dollar bonds fell after the ruling.
Residents who spoke to Nation said they were happy with the decision and some even demanded a repeat of the entire six elections.