Mr Annan, on his fifth day in the country, was to continue meetings in the capital as security forces patrolled the western Rift Valley's volatile towns of Nakuru and Molo, where the latest round of killings left at least 15 dead.

Long-festering tribal tensions burst out into violence following charges that President Mwai Kibaki stole the Dec 27 presidential polls from opposition chief Raila Odinga, plunging the nation into a vortex of violence.

The death toll from weeks of violence has topped 800 and is rising.

What started as post-election riots rapidly descended into settling of tribal vendettas, with marauding gangs armed with machetes, metals bars, bows and arrows stalking parts of the west of the country, which until the crisis was seen as a beacon of democracy and stability in the troubled east African region.

International mediators have failed to make headway in the crisis marked by the rape of women, burning of trading posts, slums and rural houses, derailing of trains and police killing of looters as well as tear gassing opposition marchers.

Symbolic first meeting
On Thursday, Mr Annan organised a symbolic first meeting between Mr Kibaki and Mr Odinga, who shook hand, called for peace and hinted at a willingness to talk, but the gesture was later undermined by further squabbling and maintaining hardline positions.

'The meeting was an important first step to launch a process of dialogue on a political solution to the elections crisis,' US State Department deputy spokesman Tom Casey said Friday in a statement.

Night-time curfew
The fighting in Nakuru, where authorities imposed a night-time curfew, pitted rival ethnic groups against each other as police struggled to end the unrest that has also left some 260,000 people displaced across the country.

Police helicopters flew over a deserted Nakuru and Molo late on Friday, as paramilitary police patrolled on the ground and army trucks drove towards the main road to Nairobi, where gangs had cut down trees to erect roadblocks.

Until recently, Nakuru, the Rift Valley's provincial capital, had a been relatively calm refuge for people displaced from elsewhere in the region.

'So far since the conflict started, we have some 5,000 camped in Nakuru and we are struggling to give them supplies,' Abdi Shakur Abdullahi, a Kenya Red Cross official, said on Friday.

'We fear that the numbers will swell if the situation does not improve.'

Disputes since 1960s
Disputes in the area stem from the 1960s when Kikuyus - Kibaki's ethnic group - acquired land but displaced the Kalenjin, leaving a grievance that has remained unresolved and has been worsened by political vendettas.

The Kalenjin mainly supported Mr Odinga, and have taken advantage of the post-poll turmoil to chase out other ethnic groups, who are now regrouping to fight back.

One Kikuyu fighter said they were seeking revenge for recent attacks.

'The government has failed to protect our people so we have decided to take revenge for our brothers killed in Burnt Forest and Eldoret,' said Amos Ndungu, referring to two Rift Valley towns and scenes of some of the worst post-poll violence.

'The Kalenjins think we fear them, but we have decided to show them that we can also kill,' Ndungu said.

The Red Cross said up to 50,000 had been displaced in Molo since the elections.

'The spiral effect of counter-attack and reprisals is getting out of hand in this area of the Rift Valley and urgent measures need to be put in place to resolve this,' said Abbas Gullet, secretary general of the Kenya Red Cross.

The International Committee of the Red Cross said it had sent medical supplies to Nakuru provincial hospital, where some 100 wounded people had been taken for treatment.

Human Rights Watch has accused opposition officials of inciting ethnically-motivated attacks in the area, especially against Kikuyus. The opposition immediately rejected the claims.

In New York, the heads of state-run Kenya National Commission on Human Rights and Kenya Human Rights Commission called on the UN Security Council to take up the ethnic strife in the east African state.

African Union summit
Meanwhile, Mr Odinga on Friday urged an upcoming African Union summit to refrain from endorsing Mr Kibaki's reelection, warning the African body would be setting a bad precedent if it endorses an 'illegitimate' government.

Mr Kibaki's comment on Thursday that he was a 'duly elected president' angered Mr Odinga's opposition Orange Democratic Movement, undermining short-lived hopes that the two foes were moving towards breaking the deadlock. -- AFP