(Karel Prinsloo ~ Associated Press)
Behind him, hundreds of angry young men -- armed with knives, machetes, saws and shovels -- scream as they watch homes burn. These men belong to Kenya's dominant Kikuyu tribe.
Across the bridge, where members of the rival Luo tribe have gathered, comes even more screaming, equally enraged.
The two groups exchange insults and stones, waiting for the other to attack. The fighting has been fierce. People are slashed with machetes, their homes torched. The desire for revenge is strong.
"Those people have burned our homes," Mugambi said of the Luos. "I will cut any who come across that bridge."
A wave of violence over a disputed presidential election has laid bare the ethnic rivalries under the surface of this East African country. The fighting has exposed tribal resentments and divisions between those who have benefited from the country's recent economic boom and those who have not.
The bloodshed has cast a dark shadow over this popular tourist destination, previously one of Africa's most stable democracies. With politicians so far unwilling or unable to control the ethnic hatreds, the violence is now raising questions over whether prosperous Kenya can keep avoiding the bloodbaths of its neighbors Rwanda, Uganda and Sudan.
At least 300 people have been killed and 100,000 displaced since Mwai Kibaki, the incumbent president and a Kikuyu, was declared the winner of the Dec. 27 presidential election by a thin margin. Fiery opposition leader Raila Odinga, a Luo, called the election a sham, and international observers also have questioned the fairness of the vote count.
Odinga's supporters, especially fellow Luos, poured into the streets even before Kibaki was announced the winner Sunday and hastily sworn in for a second term. Police shot many rioting Odinga supporters, as Luos began to torch Kikuyu homes.
Members of the two tribes have lived as neighbors. But with so many homes torched over the past few days, they are beginning to separate into enclaves.
Politics and poverty
Poverty, politics and history all play their part in this violence. Many of Kenya's 42 tribes accuse the Kikuyu, the largest tribe, of shutting others out of business and politics. Two out of three of Kenya's presidents have been Kikuyu -- though its longest-serving president, Daniel arap Moi, came from a small tribe from western Kenya.
Although Kikuyus control much of the retail sector and are proud of their reputation for entrepreneurship, they insist they don't stop anyone else from making money.
In recent years, Kenya has seen record economic growth, but the mushrooming high rises and luxury cars inspired resentment among the millions left behind. Odinga's campaign slogan was whittled down to a single cry -- "change."
"We voted for change," Odinga supporter James Okidi shouted during an opposition protest. "If Kibaki can't give us our president, the mortuaries are not yet full," Okidi said.
, one of hundreds of thousands of impoverished, unemployed young men living in Kenya's most desperate areas.
In perhaps the most horrific attack, a church in Eldoret, 180 miles west of the capital, was set on fire Tuesday with dozens of Kikuyus -- including children -- inside. As many as 50 people were killed, witnesses said.
But the violence is not confined to the Kikuyus and Luos. Anyone who is from a region perceived to have voted for the other candidate is a target.
Thieves and thugs have also compounded the chaos. A feared Kikuyu criminal gang, the Mungiki, has re-emerged in the slums after a police crackdown last year.
A recruiter for the Mungiki gang, which is blamed for a string of beheadings last year, said residents were appealing for help. Fearing arrest, the recruiter refused to give her name.
With police unable to control the violence, the Kikuyus say they will defend themselves.
"When you're pushed in a corner, you will fight," said 20-year-old Marvin Gicheha, a Kikuyu in Mathare, the Nairobi slum where Mugambi lives.
Around Gicheha, hundreds of young people carrying axes and machetes poured from smoky alleyways where shopkeepers, short on water, vainly threw tins of paint and buckets of raw sewage on their flaming shops. A man lay in the road in puddles of blood from deep gashes on his head and hands, a few yards from where riot police fired in the air, trying to separate rival groups.
The opposition and the government blame each other for the violence.
"We wish to condemn most strongly the acts of genocide being perpetrated in parts of the Rift Valley," said Land Minister Kivutha Kibwana.
He blamed the opposition, but as the bullet-riddled bodies of protesters piled up in the morgues, Odinga visited The Associated Press to denounce "genocide" by the government against his own supporters.
Dr. John Okello, who works at Nairobi hospital, said criminals had taken advantage of the chaos to rape and loot. The number of rape victims admitted to the hospital has soared, and hospitals are running out of bandages because they have so many trauma victims, he said.
"It's a cycle of fighting and revenge," Okello said as he watched black smoke billow from the slums. "The politicians can't stop it now."