Kenya has declared Thursday a public holiday to celebrate the election of Barack Obama to the US presidency.
"We the Kenyan people are immensely proud of your Kenyan roots," President Mwai Kibaki said.
The BBC's Juliet Njeri says Mr Obama's step-grandmother was seen dancing and cheering jubilantly outside her house after the results were declared.
She says Mr Obama's family stayed up all night in the western Kenyan village of Kogelo watching the election count, and they are now preparing for a big party.
 |  Your victory has demonstrated that no person... should not dare to dream of wanting to change the world for a better place  Nelson Mandela  |
Nelson Mandela, South Africa's first black president, welcomed Mr Obama's victory as a sign of hope for everyone.
"Your victory has demonstrated that no person anywhere in the world should not dare to dream of wanting to change the world for a better place," he said in a letter of congratulations.
Unifying
In Kisumu city, near the Obamas' home village, there is a carnival atmosphere and people have poured onto the streets singing Mr Obama's praises, our reporter says.
|  Kogelo residents speak of their joy over Barack Obama's victory   |
In January, Kisumu was the scene of running battles between members of the public and police after riots broke out over the Kenya's contested elections.
But correspondents say the US election seems to be a unifying moment for the country, with people reported to be saying that Mr Obama's victory is a victory for all Kenyans.
In the capital, crowds were seen singing and dancing, waving branches and carrying posters of Mr Obama along Ngong Road, one of Nairobi's major highways.
"Your victory is not only an inspiration to millions of people all over the world, but it has special resonance with us here in Kenya," Mr Kibaki said.
