Uhuru Kenyatta Kenya's deputy prime minister, has asked the international community to respect the democratic will of the Kenyan people after winning the country's presidential election.
Kenyatta faces trial for crimes against humanity in July at the International Criminal Court (ICC) over violence that took place in the aftermath of the country's previous election in 2007.
In his acceptance speech on Saturday, Kenyatta called for unity and pledged co-operation with international institutions but also said that he expected the world to respect Kenya's sovereignty.
"Today we celebrate the triumph of democracy, the triumph of peace, the triumph of nationhood," he said.
"My pledge to you is that as your president I will work on behalf of all citizens regardless of political affiliation.
"I will honour the will of Kenyans and ensure that my government protects their rights and acts without fear or favour, in the interests of our nation."
Kenyatta was named the winner of the election after gaining 50.07 percent of the vote, but his opponent, Raila Odinga, the country's prime minister, has refused to concede, alleging multiple failures in the election's integrity that he said has put Kenyan democracy on trial.
Al Jazeera's Mohammed Adow, reporting from Nairobi, said that Kenyatta's call for unity illustrated that with such a slim margin of victory, the new president knows he will have to work to earn the trust of Kenyans who cast their ballots for other candidates.
Speaking after his opponent, Kenyatta, called last week's polls, "the most free, the most fair, election in Kenya's history."
Kenyatta also thanked his "older brother, Raila Odinga, for his spirited campaign" and said that now is the time for all Kenyans to come together.
In Odinga's hometown of Kisumu in Western Kenya, riot police were deployed after supporters burnt tyres and logs to block traffic.
Arguing the vote was rigged, they chanted chanted: "No Raila, No Peace."
Kenyatta is accused of hiring the quasi-cult criminal Mungiki fraternity to target Luo groups and villages in the aftermath of the disputed poll in 2007. He denies the charges and has asked for the trial to be delayed.
The US, Britain and the European Union have given new leader a chilly reception.
All released statements congratulating the Kenyan people but none mentioned Kenyatta by name.
The West had made it clear before the vote that it would not welcome a Kenyatta victory, with Washington previously warning of "consequences''.
Kenya will now become the second African country after Sudan to have a sitting president indicted by the ICC.
Kenyatta, as president, may have to spend large chunks of his first years in Kenya's highest office in a courtroom in The Hague, where the ICC is based in the Netherlands.
Odinga's camp had said during tallying that the ballot count was deeply flawed and had called for it to be halted.
Speaking in the Kenyan capital on Saturday, Odinga said "rampant illegality" across the entire election process had led him to seek a Supreme Court investigation into polling procedures.
Saying almost "every instrument" of the Independent Electoral and Boundaries Commission had failed, Odinga cited a lowering of voter registrations in his coalition's strongholds as an area of concern.
Odinga said he has "no other interests" other than to know if the Kenyans "want us" as their leaders.
Joyous supporters of Kenyatta thronged the streets in his tribal strongholds on Saturday following the result, lighting fluorescent flares and waving tree branches and chanting "Uhuru, Uhuru".