Defeated Kenyan presidential candidate Raila Odinga has said he challenge the result in the courts.
He urged his supporters to refrain from the violence that convulsed Kenya when he lost the disputed vote of 2007.
A smooth handover of power is seen as critical to restoring Kenya's reputation as a stable democracy and safe investment destination.
In Kisumu, the biggest city in Mr Odinga's tribal heartland, business owners made plans for a full resumption of trading after many had run down their stocks in the run-up to the vote because of fears of unrest and looting.
Nestled on the shores of Lake Victoria in the west of Kenya, Kisumu was a flashpoint in the post-election violence five years ago that left more than 1,200 people dead, hundreds of thousands uprooted from their homes and properties destroyed.
Uhuru Kenyatta avoided a run-off vote by a razor-thin margin, just edging above the 50% mark, meaning he won outright.
The tiny margin was enough to raise concerns that Mr Odinga supporters could take to the streets, even though Mr Kenyatta was more than 800,000 votes ahead of his rival.
Western nations now face a diplomatic dilemma about how to deal with a president who is indicted for crimes against humanity.
Mr Odinga said that the election was "tainted", an echo of his claims that the 2007 vote he lost to the now-outgoing president, Mwai Kibaki, was stolen.
But he also said he would fight it in the courts, not on the streets.