ELDORET, Kenya — A policeman shot and killed an opposition lawmaker yesterday in what authorities say was a crime of passion over a woman. But machete-wielding protesters convinced it was an assassination clashed with police, leaving at least three dead. The fighting interrupted talks aimed at calming a nation gripped by violence since a disputed election a month ago.

Police said David Too was shot by a police officer who discovered the lawmaker was having an affair with his girlfriend. The woman — whom Too family members deny was linked to the politician — was shot in the same attack and also died, a hospital official said.

Too was the second anti-government legislator killed in a week; opposition politicians said both were victims of assassination plots.

Kenya has been embroiled in ethnic violence since President Kibaki was declared the winner of the December 27 election and opposition candidate Raila Odinga, who is head of Too’s party, rejected the result, saying the vote had been rigged.

Much of the bloodshed has pitted other tribes, including Mr. Odinga’s Luo, against Mr. Kibaki’s Kikuyu people. Kikuyus, Kenya’s largest ethnic group, have long been resented for their dominance of the economy and politics. Western Kenya’s Rift Valley has seen some of the worst violence.

Mr. Odinga has said he wants a new election, while Mr. Kibaki has made clear he will not negotiate his position as president.

In Nairobi, negotiators from the two camps began the first day of talks mediated by a former secretary-general of the United Nations, Kofi Annan. But the talks were delayed after a morning session, with Mr. Annan saying leaders needed to calm their followers following Too’s death.

“We will postpone our session this afternoon and work all day tomorrow so they can attend to urgent matters,” Mr. Annan said.

Too’s death came two days after another opposition lawmaker, Mugabe Were, was fatally shot as he drove to his house in suburban Nairobi, setting off more violence. The opposition party secretary-general, Anyang Nyongo, said there was “an evil scheme” to kill legislators and rob the opposition of its majority in Parliament. Legislative elections held the same day as the presidential vote gave the opposition 99 Parliament seats to 43 for Mr. Kibaki’s party. Were and Too would have been freshmen lawmakers.