NAIROBI, Kenya — Kenya, once a leader in the region, is following neighbors like Somalia down a path of disintegration, with no solution in sight as burning slums and thousands fleeing in fear alter the nation's ethnic map _ perhaps forever.
Police in helicopters on Tuesday fired to turn back mobs. 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."
The international community is pressuring Kibaki and his chief rival Raila Odinga _ who is a member of the Luo tribe _ to share power to end the crisis over the disputed presidential election.
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."
"We must not look back years from now and wonder how and why things were permitted to go so horribly wrong," Obama said in a statement he read on Capital FM radio.
Secretary of State Condoleezza Rice called the violence "deeply concerning," saying, "We are currently asking everyone to maintain calm."
Political disputes in Kenya often mushroom into ethnic clashes, but never before with the ferocity that has left more than 800 people dead since the Dec. 27 election that the international community and many Kenyans agree had a rigged vote tally.
It was only the second free election in Kenya, which suffered decades under one-party and authoritarian rule.
Kibaki, whose insistence that he is president has incited some of the violence, on Tuesday deplored the fact that some Kenyans "have been incited to hate one another and view each other as enemies."
Some of the violence is an expression of pent-up anger by the marginalized majority in Nairobi slums, where 65 percent of the capital's residents balance on the edge of survival. Statistics shows Kenyans growing poorer and in greater number each year while corrupt politicians who mouth pious words about alleviating poverty buy ranches in Australia and lakeside villas in Switzerland.
In the western Rift Valley, scene of the worst violence, thousands of people set homes ablaze, smashed shop windows to loot goods, and set up blazing road blocks where they hunted for rival tribespeople.
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.
In villages around Eldoret, another western town, gangs of young Kalenjins on Tuesday slashed to death four Kikuyus and stoned two others until they died, witnesses said. When a helicopter tried to land to intervene, the youths set grasslands ablaze, the witnesses said.
At the heart of the conflict are decades-old grudges over land. The Rift Valley is the traditional home of the Kalenjin and Masai. British colonizers seized large tracts of land to cultivate fertile farms there. When much of that land was redistributed after independence in 1963, President Jomo Kenyatta flooded it with his Kikuyu people, instead of returning it to the Kalenjin and Masai.
Kikuyus are Kenya's largest ethnic group, making up about 22 percent of the population of 38 million. Two of the three presidents since independence were Kikuyu and their domination of politics and the economy is deeply resented.
Human rights groups and others charge that politicians are manipulating people's anger to orchestrate much of the violence.
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.
The U.N. adviser on genocide and mass atrocities, Francis Deng, issued a warning Tuesday, saying "political and community leaders may be held accountable for violations of international law committed at their instigation."
In the Rift Valley town of Naivasha, overwhelmed police officers responded Tuesday with tear gas and live bullets. When that did not work against a mob of 5,000 Kikuyus, they flew in on three helicopters and fired into the crowd. A local newspaper reporter saw two bodies with bullet wounds, but it was unclear whether the men were killed by police on the ground or in the air.
Then the helicopters swooped down, with officers firing onto a throng of armed Kikuyus pinning down hundreds of Luos outside the Naivasha Country Club, according to the local reporter. Kikuyus, armed with machetes and nail-studded clubs, had prevented the Luos from escaping for two days.
Police chief Grace Kakai said the helicopter passes helped evacuate the Luos to safety behind the walls of the prison compound. She denied that her officers fired into the crowd. "We were trying to scare them, not hurt them," she said.
Police, who initially denied killing anyone, have acknowledged they have fatally shot more than 80 protesters. Human rights defenders say the number is much higher.
The police force itself risks falling apart along ethnic lines, with some officers threatening to come to blows and even kill each other over what human rights officials charge are shoot-to-kill orders, according to police officers who have spoken on condition of anonymity for fear of losing their jobs.
Kenya's once-thriving tourist economy has been devastated by the crisis and tens of thousands of workers have lost their jobs.
Associated Press writers Katy Pownall in Naivasha, Katharine Houreld in Kisumu, and Tom Maliti, Malkhadir M. Muhumed and Tom Odula in Nairobi contributed to this report.