In the past week, Kikuyus have been taking revenge and violently expelling other ethnic groups from Kikuyu-dominated areas. Kenya seems to be tearing itself apart along ethnic lines, with more than 800 people killed and at least 300,000 displaced.  The State Department spokesman, Sean McCormack, said Ms. Frazer had made the assessment based on “her firsthand view of the situation,” but did not say whether the department would adopt her use of the term ethnic cleansing. Rather, he said the department was collecting information on “any atrocities that may have occurred.”  The term gained currency during Yugoslavia’s civil war in the early 1990s. There are many definitions, but it is widely used to mean creating an area that is ethnically homogenous by using force or intimidation to remove people from another ethnic or religious group.  That seems to be the case in many towns and neighborhoods in Kenya, and it shows no signs of letting up. On Wednesday, Kikuyu residents of a town called Kikuyu massed in the streets and demanded that Luos, Mr. Odinga’s ethnic group, leave. Dozens of Luos were hiding in a government building. Police officers put them in a bus and escorted them away. Many residents cheered.  Kofi Annan, the former United Nations secretary general, is brokering talks between Kenya’s opposing politicians and has emphasized that time is running out. Residents across Kenya have talked about meetings where community elders have mapped out plans to kill and drive out members of rival ethnic groups.  Ms. Frazer is one of the first high-ranking Western officials to apply the term ethnic cleansing to Kenya. Many diplomats have shied away from it, saying its use could increase tensions and give the impression that the diplomats were taking sides. The government accuses opposition leaders of orchestrating mayhem and engineering ethnic cleansing of groups that back the president; the opposition counters that the violence was spontaneous outrage over a rigged election.  Government officials seemed pleased by Ms. Frazer’s statement. “This is what we have been saying all along,” said a spokesman, Alfred Mutua.  He said that government lawyers were collecting evidence against ringleaders for use before the International Criminal Court. “We don’t want this to seem political,” Mr. Mutua said.  Salim Lone, a spokesman for Mr. Odinga, disagreed with using the term. “Most knowledgeable observers have characterized these killings as political rather than ethnic,” he said. “But there is no doubt that their terrifying scale and brutality have engendered deep communal hatreds on both sides. That is why it is so vital that both sides to the electoral dispute do everything possible to make Mr. Kofi Annan’s mediation efforts succeed by making an uncompromising and unconditional commitment to peace.”  Mr. Lone said that the negotiations, which began formally on Tuesday, had gotten off to a good start and that Mr. Kibaki helped eased tensions by allowing Mr. Annan to sit in the middle of a dais, which sent the signal that Mr. Annan, not Mr. Kibaki, was leading the meeting.  The country, meanwhile, seemed to be in a tense simmer on Wednesday, with few major episodes of violence reported but standoffs continuing between gangs of opposing ethnic groups.  Government officials said that they were continuing to investigate the killing of Melitus Mugabe Were, a freshman member of Parliament, who was shot to death in his driveway on Tuesday morning. But it seems that the case is only getting murkier.  A local newspaper reported that his wallet was stolen, implying a possible robbery, but his brother-in-law, Vincent Nyabeii, said that was not true. “Nothing was taken, nothing,” he said. “This was an assassination.”  Many supporters have said Mr. Were, a self-made businessman who was revered in the slum where he grew up, was killed by thugs employed by the government because he was a member of the opposition. If he was eliminated and a new election was held, his supporters said, his seat would probably go to a member of the government’s party.  But it is not clear how solid an opposition member he was. He was a moderate by all accounts and was seen as a potential peacemaker. Members of Mr. Kibaki’s party said Mr. Were was even considering defecting, which could have tipped the balance of power in Parliament, where the opposition has a slight edge. On Wednesday, one government official said that right before the killing, Mr. Were made an appointment to meet with the president and that he might have been slain by people in his own party who saw him as a traitor.  Several of Mr. Were’s friends have said that he was disillusioned with his party’s response to the disputed election, especially the calls for protests, which have resulted in many people being killed, including some shot by police officers. “He was not in thick of his party’s politics,” said George Kimani, a friend.  As for the possibility of defection, Mr. Kimani said, “Yes, he was considering it.”  Kennedy Abwao contributed reporting from Addis Ababa, Ethiopia.  A version of this article appears in print on , on Page A3 of the New York edition with the headline: U.S. Envoy Calls Some Kenya Violence Ethnic Cleansing. Order Reprints| Today's Paper|Subscribe
The top American diplomat for Africa said that some of the violence that has swept across Kenya in the past month was ethnic cleansing.