At least two people have been shot dead during protests following the re-election of President Uhuru Kenyatta.
Four people were also injured after opposition supporters staged protests at the outcome of the election, which they claim was rigged.
The demonstrations have largely taken place in opposition strongholds, but have generated comparisons with the disputed 2007 election which led to two months of ethno-political violence that left 1,100 people dead.
Opposition candidate Raila Odinga claimed his loss was down to vote rigging and said the election was a “charade”.
The 72-year-old politician has now had four unsuccessful attempts to win the presidency.
Protests in the Kawangware slum in Nairobi have left burning tyres, debris and looted shops following running battles between opposition supporters and police.
In Kisumu, three men were treated in hospital after they were shot by police. Two men also sustained gunshot wounds in Mathare slum.
The country’s election commission said Mr Kenyatta won the election with 54.27% of the vote, calling it “credible, fair and peaceful”.
Mr Odinga took 44.74%, according to commission chairman Wafula Chebukati.
Nearly 80% of the 19 million registered voters cast their ballots.
Mr Kenyatta, 55, is a wealth businessman and the son of Kenya’s first president.
He called for unity this week, saying “there is no need for violence”.
He added: “I reach out to you. I reach out to all your supporters. To our brothers, our worthy competitors, we are not enemies, we are all citizens of the same republic.”