A mob torched a church sheltering hundreds of people fleeing election violence Tuesday, killing up to 50 people — including many children — as four days of rioting and ethnic clashes marked one of the darkest times in Kenya's history.

President Mwai Kibaki, sworn in Sunday after a vote opponents said was rigged, said political parties should meet immediately and publicly call for calm. The violence has killed at least 270 people in what had been east Africa's most stable and prosperous democracy. The opposition candidate, Raila Odinga, said he would refuse to meet.

• Click here to view photos.

"If he announces that he was not elected, then I will talk to him," Odinga told The Associated Press. He accused the government of stoking the violence, and said Kibaki's administration "is guilty, directly, of genocide."

The election commission chairman said Tuesday he had been under intense pressure from both sides to announce the vote results quickly.

Violence erupted throughout Kenya, from the shantytowns of Nairobi to resort towns on the sweltering coast, exposing festering tribal resentments. Kibaki's Kikuyu people, Kenya's largest ethnic group, are accused of using their dominance of politics and business to the detriment of others.

Odinga is from the Luo tribe, a smaller but still major tribe. In the slums, which are often divided along tribal lines, rival groups have been going at each other with machetes and sticks, as police fire tear gas and live rounds to keep them from pouring into the city center.

The church fire in Eldoret, some 185 miles from the capital, killed at least 50 people, said a Red Cross volunteer who counted the bodies and helped the wounded. But she asked that her name — which would identify her tribe — not be published, saying gangs were even checking on the tribal affiliations of aid workers.

Anne Njoki, a 28-year-old Kikuyu, said she fled her home in the slums after she saw Kikuyus being attacked and their homes looted. She was camped out near a military base with her sister, 3-year-old nephew and 7-year-old niece.

"They have taken our beds, blankets, even spoons," she said of the looters. The children had not eaten for days.

The European Union and the United States have refused to congratulate Kibaki, and the EU and four top Kenyan elections officials have called for an independent inquiry.

In Britain, Prime Minister Gordon Brown urged Kibaki and Odinga to hold talks.

"The violence must be brought to an end," he said Tuesday in London.

Also Tuesday, Odinga insisted he would go on with plans to lead 1 million people in a protest march in the capital Thursday against Kibaki, who had been trailing Odinga in early election results and opinion polls before pulling ahead.

The government banned the demonstration, but Odinga said: "It doesn't matter what they say."

Election commission chairman Samuel Kivuitu said he had been pressed by both the opposition and Kibaki's Party of National Unity to make the election results public.

"I was being pushed by PNU and ODM-Kenya (the opposition party) to announce the results immediately," Kivuitu said, while Western ambassadors "wanted me to delay announcing the results, even if it is for a week," to allow the commission to go through allegations of irregularities.

Kivuitu told reporters he even contemplated resigning, but stayed on because "people would think I am afraid of what is happening," according to comments broadcast by private TV channel KTN.

The widespread violence and gathering international pressure could lead Kibaki to seek a compromise with the opposition. Riots also have been raging in opposition strongholds in western Kenya, the tourism-dependent coast and the Rift Valley.

In Nairobi's Mathare slum, Odinga supporters torched a minibus and attacked Kikuyu travelers, witnesses said Tuesday.

"The car had 14 people in it, but they only slashed Kikuyus," witness Boniface Mwangi said. Five were attacked by the machete-wielding gang, others robbed, he said.

In Nairobi's slums — home to a third of the city's population — parents searched for food, with many shops closed because of looting.

Winnie Nduku, 34, said she and her three young children had not eaten in three days and the family had no money because her husband, a minibus driver, could not get to work.

"My eldest daughter keeps asking what am I going to do, and the small one is crying from hunger," she said.

Kibaki, 76, won by a landslide in 2002, ending 24 years in power by Daniel arap Moi. Kibaki is praised for turning the country into an east African economic powerhouse with an average growth rate of 5 percent, but his anti-graft campaign has been seen as a failure, and the country still struggles with tribalism and poverty.

Odinga, 62, cast himself as a champion of the poor. His main constituency is the Kibera slum, where some 700,000 people live in poverty, but he has been accused of failing to do enough to help them in 15 years as a member of parliament.