Up to 50 people were burned to death when a church was torched by a mob in ethnic violence that followed Kenya's disputed election.

Witnesses said dozens of people including children, who were seeking refuge in the church, were burned or hacked to death with machetes in the Rift Valley city of Eldoret.

The attack brought the death toll from four days of rioting to more than 275.

President Mwai Kibaki, sworn in on Sunday after a vote opponents said was rigged, said political parties should meet immediately and publicly called for calm.

But opposition leader Raila Odinga said he would refuse to meet the president to try to end the chaos unless President Kibaki accepted his election was illegitimate.

The violence erupted throughout Kenya, from the shanty towns of Nairobi to resorts on the sweltering coast, exposing tribal resentments that have long festered in the country.

Meanwhile, efforts to secure a peaceful resolution to the escalating violence will continue today as Britons holidaying in the African country are warned to stay indoors.

Foreign Secretary David Miliband and US Secretary of State Condoleezza Rice issued a joint statement calling for the cessation of violence and pledging the support of "diplomatic and political efforts" from Britain and the US.

Around 7,000 Britons are currently in the country.