Kenya's Supreme Court has upheld Uhuru Kenyatta's narrow election victory over incumbent president Raila Odinga in the recent elections.
The six-member bench's verdict was unanimous, and said the polls were conducted in a "free, fair, transparent and credible manner in compliance with the constitution and all relevant provisions of the law".
Petitions filed by other civil society groups have also been dismissed by the court.
"It is now for the Kenyan people, their leaders, civil society, the private sector and the media to discharge (their duty), to ensure that the unity, peace, sovereignty and prosperity of the nation is preserved," said Chief Justice Willy Mutunga.
Kenyatta, along with the vice-president-elect William Ruto, is expected to be sworn in on 9 April.
In a BBC interview, Odinga said that he has accepted the top court's ruling to avoid bloodshed, but vowed to fight on through peaceful means.
He said: "I am going to tell my people to look at peaceful ways of resolving this issue. The Supreme Court is just one step, there are many other avenues. Wounds have not been healed; in fact they've been opened up by what's happened."
The presidential elections on 4 March produced a narrow win for Kenyatta which was later challenged by the former prime minister Odinga. Kenyatta won 50.07 percent against Odinga's 43.28 percent, avoiding a run-off by 8,100 votes.
Minor clashes erupted soon after the announcement. Two people were killed and nearly a dozen injured during skirmishes in the western city of Kismu, an Odinga stronghold. Police fired shots in the air and used tear gas to control the situation.
"The court has now spoken. I wish the president-elect, honourable Uhuru Kenyatta, and his team well," Odinga said in a televised address.
Violent protests in 2007 following the election claimed the lives of 1,200 people.
Western powers were cautious in congratulating Kenyatta, who faces charges of crimes against humanity in the International Criminal Court.
"We also congratulate the people of Kenya on the peaceful conduct of the election and commend Raila Odinga for accepting the Supreme Court's decision. We urge all Kenyans to peacefully accept the results of the election," said the White House.
David Cameron and European Union President Jose Manuel Barroso have also welcomed the new government in Kenya.