Kenya's President Uhuru Kenyatta has been re-elected following Tuesday's election, officials say.
Mr Kenyatta, in office since 2013, took 54.3% of votes, ahead of his rival Raila Odinga, with 44.7%.
After the announcement, Mr Kenyatta called for unity, telling opposition supporters: "I reach out to you... We are all citizens of the same republic".
But the opposition rejected the results even before they were declared, calling the process a "charade".
However, it has been endorsed by international observers. Mr Kenyatta said they had ensured a "free, fair and credible election".
Angry protests have started in the city of Kisumu - an opposition stronghold - and in various slums of the capital Nairobi, including Kibera, where businesses are said to have been attacked.
Police, who were deployed in anticipation of the results, have fired tear gas in several locations.
Fires have been lit by protesters on a road in the heart of Kisumu, a BBC reporter at the scene says. Gunshots have also been heard.
Earlier, Mr Odinga's supporters said he had won, and published their own figures. The electoral commission said this was "illegal and premature", and said basic mathematical errors had been made.
Many observers fear a repeat of the violence after the disputed election 10 years ago, when more than 1,100 Kenyans died and 600,000 were displaced.
Mr Kenyatta has urged peace. "We have seen the results of political violence. And I am certain that there is no single Kenyan who would wish for us to go back to this," he said.
Ahead of the results, Mr Odinga had called on his supporters to remain calm, but added that he did not control anyone, and that "people want to see justice".