ADDIS ABABA, Ethiopia - The top U.S. envoy to Africa called the month of post-election violence in Kenya "ethnic cleansing" and said Wednesday Washington was reconsidering hundreds of millions of dollars in aid to the country.

Jendayi Frazer said neither President Mwai Kibaki nor his chief rival, opposition leader Raila Odinga, is doing enough to stop the bloodshed that has claimed more than 800 lives since the disputed Dec. 27 presidential vote.

Much of the violence has pitted other tribes, including Odinga's Luo, against Kibaki's Kikuyu who are the largest ethnic group. Kikuyus have long been resented for their dominance of Kenya's economy and politics, but poor Kikuyu are among the slum dwellers who have been left out of the country's economic boom.

Frazer said the violence she saw during a visit earlier this month to the western Rift Valley pitted the Kalenjin, who support Odinga, against Kikuyus.

"The first wave of this violence, it was primarily in the Rift Valley, and it was Kalenjin pushing out Kikuyu. But that may now be spreading to Kikuyus pushing out Luos and Kalenjins," Frazer told reporters in Addis Ababa, Ethiopia on the sidelines of an African Union summit.

"What I was talking about in terms of the ethnic cleansing that I saw was the immediate aftermath of the election, in which there was an organized effort to push people out of the Rift Valley." In that area, she said people were told to leave their homes on the threat of death if they did not flee.

Frazer said she did not consider the killings a genocide.

Kikuyus were the major victims of the first explosion of violence after the announcement that Kibaki had won the election, which the international community and election monitors agree was rigged.

Hundreds of Kikuyus have been killed, and members of the group account for more than half of the 255,000 chased from their homes, most in the Rift Valley.

In the Rift Valley, decades-old grudges over land are at the heart of the conflict. The valley is the traditional home of the Kalenjin and Masai people. 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.

Some of the violence is an expression of long pent-up anger by the marginalized majority in Nairobi slums, where 65 per cent of the capital's residents teeter are struggling just to survive.

Human rights groups and others accuse politicians of orchestrating the violence.

Frazer said neither Kibaki nor Odinga, who says he won the election, have done enough to halt the violence. She said speeches made by both had proved counterproductive.

"I think both sides have spent quite a lot of time, and unhelpful time, in the public," Frazer said.

"We're calling for an investigation into the inciting of violence as well as an investigation into who is actually killing people," Frazer said. "We know there have been politicians on radio inciting violence before the election ended."

Frazer said the United States was reviewing all its aid to Kenya, expected to amount to more than $540 million this year, even though most goes to the people not to the government. She acknowledged that most U.S. funds in Kenya are used to fight AIDS and malaria and go to non-governmental organizations.

"It will be counterproductive of us to stop the HIV/AIDS program when the population is in crisis," she said.

Nevertheless, "we are in a process where we are looking at all of our aid to Kenya," Frazer said, reiterating that the U.S. is "putting on the table all of our activities in Kenya to review."

The United States previously had said it would not threaten deep aid cuts.

Targeting aid is part of the pressure the international community is bringing to bear on Kibaki and Odinga to share power to end the crisis.

Former UN 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.

The European Union and other countries, including Canada, have already warned that they will cut aid if the rival sides do not make progress in resolving the crisis.

Casualties of the conflict mounted on Wednesday when six charred, slashed bodies were brought to the Nairobi mortuary after a night of violence in the slums sparked by the death of an opposition legislator.

On Tuesday, gunmen killed opposition legislator Melitus Mugabe Were as a drove up to the gates of his Nairobi home. Groups of armed youths began gathering after the shooting in the capital's Mathare and Kibera slums, and clashes, arson and looting ensued.

The six bodies brought to the Nairobi mortuary were both Kikuyu and Luo and all came from Kibera, according to a morgue attendant.

In the Rift Valley, an Associated Press reporter saw the charred body of a Kikuyu killed Wednesday in an outlying slum of Kisumu. Witness Johnson Omondo said a crowd of Luos had demanded the man's ID card, determined from his name he was Kikuyu and killed him. Another charred body, also Kikuyu, lay in the street of a neighboring slum.

At the Kenya Research Forestry Institute, about 300 unarmed Kikuyus gathered to demand that a couple hundred Luo people working there leave. They set ablaze a field of grass that was part of an animal feed research project.

Police escorted a bus full of women and children out of the institute.

When the crowd threatened to storm the building, police fired live bullets over their heads.

Inside, men in business suits armed themselves with machetes and iron bars.

"People don't want them (Luos) here," said Kamau George, a civil servant. "They are supposed to go back to Kisumu because they have chased our people from Rift Valley."