Gunmen killed opposition legislator Mugabe Were, and slums where a tense peace had held for days exploded with machete-wielding gangs setting fire to homes and businesses owned by President Mwai Kibaki's Kikuyu people.
Sabat Abdullah, a slum resident, said a gang dragged a Kikuyu doctor from his clinic "and then cut and cut until his head was off."
Former U.N. Secretary-General Kofi Annan is negotiating, but says it will take a year just to settle on a plan for resolving the deep-rooted problems that caused anger over the election to turn to murderous hate between neighbors of decades.
Barack Obama, the Democratic presidential candidate whose father was Kenyan, made a plea for peace Tuesday, saying "Kenya has come too far to throw away decades of progress in a storm of violence and political unrest."
A gang of Luos stoned a Kikuyu man, then slashed him with machetes and threw him to burn to death on their roadblock of flaming tires. Police took away the body.
"We didn't waste time, we had to kill him," Stanley Ochieng, 25, told an Associated Press reporter.
Odinga and Kibaki blame each other and have traded charges of "ethnic cleansing." More than 100,000 Kikuyu have fled homes in the Rift Valley — some fear they will never return, hard-liners say they never should.