Protests have erupted in western Kenya and large groups of people have clashed in the Rift Valley in further ethnic violence.
The latest clashes complicate mediation efforts by former UN Secretary General Kofi Annan.
There are reports of gangs from rival communities fighting each other with machetes, clubs, and bows and arrows in Nakuru and nearby Naivasha.
13 people were killed overnight in clashes with police in western towns. In the worst incident of the latest flare-up, eight people were burned to death locked inside one house in Naivasha
The violence since Kenya's 27 December election has now pushed the total death toll beyond 800.
Some 250,000 refugees have fled the chaos in Naivasha and Nakuru.
The dispute over President Mwai Kibaki's re-election, which the opposition says was rigged, has plunged Kenya into a spiral of violence, battering its image as an east African trade and tourism hub and one of the continent's more stable nations.
While the initial focus of protests was the tallying of the presidential vote, which local and foreign observers said was flawed, rivalries over land, business and power dating back to the beginning of independence have now come to the fore.
