Clashes between rival tribes armed with machetes and bows and arrows marked the third, the bloodiest and what the government hopes is the last day of opposition protests over Kenya's disputed presidential election.
With more than 20 people killed between Wednesday and Friday, the opposition announced a new strategy of economic boycotts and strikes to ratchet up pressure.
The US ambassador, citing "many factors and underlying grievances," compared Kenya's violence to the 1968 race riots in the United States.
At a town hall meeting on Friday for Americans in Nairobi, Ambassador Michael Ranneberger said there was "a lot of cheating on both sides" in the December 27 elections that pitted President Mwai Kibaki against opposition leader Raila Odinga.
Kibaki insists he won the election, but international and local observers say the vote count was rigged. Kibaki's power has become more entrenched and he appears unlikely to accede to demands he step down. The opposition's best hope may rest in wrangling a power-sharing agreement that might make Odinga prime minister or vice president.
The US Embassy estimates that between 23,000 and 100,000 votes separated the two candidates. "You can't have a recount and you can't have a new election ... so the two sides need to sit (together) and work things out," Ranneberger said, suggesting the best solution was for the two to share power.
Friday's deaths raised the toll to at least 22 people killed in three days of protests called by the opposition – all but five blamed on police.
A few dozen miles (kilometers) from Kenya's famed Masai Mara game reserve in Narok, Masai fighters and men from Kibaki's Kikuyu tribe battled for hours with machetes, clubs, swords and bows and arrows. Five people were killed and 25 wounded, police chief Patrick Wambani told The Associated Press. Homes and shops were set ablaze.
Elsewhere, police opened fire on protesters in Nairobi's Kibera slum, killing six people and wounding at least 10. A blood-smeared pickup truck carried the bodies of a 15-year-old girl and a young man killed there, along with wailing relatives.
"They killed my daughter. Kibaki must die," a woman screamed. She said her daughter was washing utensils on her doorstep when police opened fire and she was hit.
Skirmishes between police and thousands of demonstrators left one person dead in the coastal tourist town of Mombasa. Kenya Red Cross official Abdallah Athman said the young man killed "was running away from the police when he was shot in the back and the bullet went through his chest."
Odinga, the opposition leader, visited the hospital to see those wounded in the Kibera shootings and condemned the police, saying they "have executed innocent Kenyans – people who they vowed to serve and protect."
"We are not going to confront the police with their bullets, no, we will take people out of the streets ... We have other powers" to pressure the government, he said.
Overall, the rallies' strength had largely evaporated from the tens of thousands who turned out immediately after the elections.
More than 600 people have been killed in Kenya's election violence, according to a government commission, the worst turmoil since a failed 1982 coup attempt in which Odinga participated.
Kenyan police released their own figures Friday, saying 510 people had died in the election violence, including 82 killed by police. Police, who had earlier denied charges they had killed anyone since Kenya descended into turmoil, have recently been more forthright, and critical of protesters.
The US-based rights group Human Rights Watch said in a statement that police were behind dozens of killings and that they opened fire on both looters and opposition protesters under an unofficial "shoot-to-kill" policy.
Friday's police statement said officers were dealing with "deception and manipulation of jobless people by their leaders. Some have been coached into committing crimes" by leaders "exploiting ethnicity, religion and subjective politics."
Seven European donor nations as well as Australia and Canada said on Friday they were deeply worried by the deteriorating human rights situation. "We have seen clear and disturbing footage of the use of lethal force on unarmed demonstrators," the seven said.
Opposition spokesman Salim Lone said Odinga would call for a "boycott of companies owned by hard-liners who are around Mr. Kibaki," including one of Kenya's biggest banks, a prominent bus company and a major dairy producer. Lone also said they would work with unions "to organize strikes in selected industries." He declined to give details.
Later on Friday, Odinga met with business leaders, but neither would speak to reporters afterward.
"We are completely ready to negotiate in good faith. We want peace in the country," Lone said. "Our people are suffering."
Kibaki's government has made similar statements, but both sides appear recalcitrant and envoys from the US and the African Union have failed to even bring Odinga and Kibaki together for talks.
A group of former African presidents trying to mediate – Tanzania's Benjamin Mkapa, Mozambique's Joachim Chissano and Botswana's Ketumile Masire – met with both Odinga and Kibaki, Odinga told reporters after the meeting on Friday.
The violence tapped into a well of resentments decades in the making – of the political and economic dominance of Kikuyus at the expense of the other 41 ethnic groups; of the growing gap between the rich and marginalized poor fueled by official corruption; of land resettlement that brought hundreds of thousands of Kikuyus onto lands native to other groups.
Ranneberger indicated at the town hall meeting that the ferocity and extent of the violence may have shaken some into considering how to remedy old hurts.
"We have a lot of confidence in the underlying pillars of this country," he said. "I'm pretty optimistic the shock, to some degree, has galvanized people."
Kenya has the biggest economy in East Africa and its ports and roads serve landlocked neighbors. The United States and other donors consider Kenya a vital partner in the war on terrorism and a regional economic and military powerhouse whose stability has stood in stark contrast to war-ravaged neighbors such as Sudan and Somalia, where Islamic extremism is rife. (AP)
Kenya marks bloodiest day of protests