Gunmen killed an opposition lawmaker in Nairobi early Tuesday, an attack likely to stoke the ethnic fighting that has gripped Kenya since last month's disputed presidential election. As with the gangs that have killed rivals and torched homes in western Kenya, groups of armed youths began gathering after the shooting in the capital's Mathare and Kibera slums. Since the Dec. 27 election, the death toll has soared over 800. Two gunmen shot opposition lawmaker Mugabe Were as he drove to his house in suburban Nairobi, police said, adding they did not yet know if the political turmoil had motivated the slaying.

"We are treating it as a murder but we are not ruling out anything including political motives," Kenya police spokesman Eric Kiraithe said. "We are urging everyone to remain calm."

But a resident of Kibera, Teddy Njoroge, said houses were being set ablaze near a railway that generally divides members of President Mwai Kibaki's Kikuyu tribe from inhabitants of opposition leader Raila Odinga's Luo ethnic group. Flames and smoke rose from one area of Kibera.

"They have decided to revenge this MP," Njoroge said of the member of parliament.

Were was among a slew of opposition members who won seats in the December legislative vote, held at the same time as the presidential election.

The killing came a day after thousands of machete-wielding youths hunted down Kikuyus in western Kenya's Rift Valley, burning homes and buses, clashing with police, and blocking roads with blazing tires.

Witnesses described seeing two people pulled from cars and stoned to death, while another was burned alive in a minibus.

"The road is covered in blood. It's chaos. Luos are hunting Kikuyus for revenge," said Baraka Karama, a journalist for independent Kenya Television in Kisumu.

The Rift Valley is home to the Kalenjin and Masai ethnic groups. British colonizers seized large tracts of land to cultivate fertile farms there. After independence in 1963, President Jomo Kenyatta flooded reclaimed farmlands with his Kikuyu people, creating deep-seated resentment that exists to this day.

Kikuyus also are resented for their domination of politics and the economy, a success cemented by endemic corruption and a patronage system where politicians favor their own ethnic group.

More than half the 255,000 people driven from their homes this month have been Kikuyus displaced in the fertile Rift Valley, an area famous for its farmland and wildlife frequented by tourists.

The bloodshed has transformed this once-stable African country, pitting longtime neighbors against one another and turning tourist towns into no-go zones.

Kibaki and Odinga blame each other for the violence, trading accusations of "ethnic cleansing." Human rights groups and officials charge it has become organized.

"What is so alarming about the last few days is ... there's evidently hidden hands organizing it now," Britain's visiting minister for Africa, Mark Malloch-Brown, told reporters Monday.

He spoke after meetings with Odinga, Kibaki and their mediator, former U.N. Secretary-General Kofi Annan.

Annan announced in a statement released Tuesday that the "dialogue process" to help resolve the deadly dispute will start Monday.

Kibaki and Odinga had been asked to name three negotiators each to participate in the talks. They are under international pressure to form a power-sharing government.

In the past, Kibaki has said he is open to direct talks with Odinga but that his position as president is not negotiable. Odinga says Kibaki must step down and only new elections will bring peace.

On Monday, columns of smoke rose from burning homes in Kisumu, according to journalists who flew into the town.

"We wish to find one, a Kikuyu. ... We will butcher them like a cow," said David Babgy, 24, who was among 50 young men stopping buses at a roadblock of burned cars and uprooted lamp posts.

But the majority of the deaths reported there Monday were people shot by police whom human rights groups accuse of using excessive force.

In Nakuru, provincial capital of the Rift Valley, 64 bodies believed to be those of Kikuyus were counted Monday at the morgue, said a worker who asked that his name not be used because he was not authorized to speak to the media.

In the past, Kibaki has said he is open to direct talks with Odinga but that his position as president is not negotiable. Odinga says Kibaki must step down and only new elections will bring peace.

On Monday, columns of smoke rose from burning homes in Kisumu, according to journalists who flew into the town.

"We wish to find one, a Kikuyu. ... We will butcher them like a cow," said David Babgy, 24, who was among 50 young men stopping buses at a roadblock of burned cars and uprooted lamp posts.

But the majority of the deaths reported there Monday were people shot by police whom human rights groups accuse of using excessive force.

In Nakuru, provincial capital of the Rift Valley, 64 bodies believed to be those of Kikuyus were counted Monday at the morgue, said a worker who asked that his name not be used because he was not authorized to speak to the media.

At least 22 people were killed in Naivasha over the weekend, said district commissioner Katee Mwanza. Nineteen of them were Luos whom a gang of Kikuyus chased through a slum and trapped in a shanty that they set on fire, said police commander Grace Kakai.

As youths set buses ablaze at Kisumu bus station Monday, police used tear gas, then opened fire. A morgue attendant said one man whose body was brought in had been shot in the back of the head. A school janitor also was killed by a stray bullet fired by a police officer, said Charles Odhiambo, a teacher at Lion's High School.

Fred Madanji, a gas station attendant, said he saw two other "protesters" shot in the back and killed as they ran from police.

In villages around Eldoret, another western town, gangs of young Kalenjin killed four Kikuyus with machetes and stoned to death two others they had pulled from cars, according to witnesses. A military helicopter tried to land at the village of Cheptiret but was prevented by youths who set grasslands ablaze.

Naivasha, Kenya's flower-exporting capital on a freshwater lake inhabited by pink flamingoes, became a war zone Monday where some 2,000 people from rival ethnic groups faced off, taunting each other with machetes and clubs inset with nails.

Each time they approached each other, a handful of police holding a line between them fired live bullets into the air. They retreated, only to regroup.

"We want peace, but we (also) want to fight them," said Peter Mwangi, 20. "We don't want Luos here," he said.

"This is Kikuyu land!" they cried, calling for revenge.

State Department spokesman Sean McCormack said Kenya has "gone from bad to worse, in terms of the violence."

European Union foreign ministers issued a statement indicating development aid could be pulled if Odinga and Kibaki don't agree to a power-sharing pact. But only about 6 percent of Kenya's budget comes form foreign aid, and the government has said it will not be blackmailed.

The United States expects to provide Kenya with more than $540 million in assistance this year, but the vast majority of that is for humanitarian programs with the largest chunk, $481 million, going for HIV/AIDS projects.

Less than 2 percent of the total, which is allocated for counterterrorism and military training, would be considered for cuts should Washington decide to review its assistance, according to the State Department.

"I think it's pretty safe to say anything dealing with trying to improve the humanitarian situation in Kenya, including the AIDS funding, is just off the table," McCormack said Jan. 17. "That's not going to happen."

Presidential spokesman Isaiya Kabira said Kibaki was likely to attend an African Union summit that starts Thursday in Addis Ababa, in keeping with steps he has taken - such as filling key Cabinet posts - that underscore his position he is the legitimately elected leader.

Odinga's party had argued that the pan-African organization should not welcome Kibaki.

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Associated Press writer Matthew Lee in Washington contributed to this report.

Written By KATHARINE HOURELD