As police appear seemingly powerless to intervene, in most cases, Kenya's opposition called for African Union peacekeepers to deploy and restore order.

"We need African Union peacekeepers to bring calm and peace. Given the ethnic dimension of the conflict, it would be more neutral than to selectively place the army," Orange Demoncratic Movement spokesman Tony Gachoka said.

The government was not immediately available for comment.

Scores of people fled ethnic attacks on their homes in heavily armed police convoys.

A Reuters reporter saw police fire shots to disperse a gang manning a roadblock, allowing a busload of refugees to flee to safety, a day before former U.N. Secretary General Kofi Annan was due to reopen talks trying to end a bloody political crisis.

Around 900 people have been killed and more than a quarter of a million uprooted since violence flared in Kenya after President Mwai Kibaki was returned to power in a December 27 vote that opposition challenger Raila Odinga says was rigged.

Annan persuaded the rival parties on Friday to agree to take quick steps to end the violence, but ethnic tension remained explosive over the weekend. Aid workers estimate at least 20 people have been killed in clashes since Thursday.

"We're just keeping the peace around here," said Charles Cheriot, at a roadblock where youths sharpened machetes on rocks and lined up arrows they said were poisoned. "The police have taken sides. We just patrol."

At a hospital in the southern Rift town of Kisii, scene of the latest clashes between Kalenjin and Kisii ethnic groups, staff said injured people were streaming in.

"Over the past 48 hours we've had 21 people come in, all but one of them with arrow wounds," Kisii hospital superintendent Dr Wycliffe Mogoa told Reuters at the hospital.

"It has been bad. All these arrow wounds -- you have to open up the wounds then remove the arrows. But we've managed," he said, adding that one person had died by a gunshot on Thursday.

Waiting for surgery to remove an arrow stuck in his arm, Phillip Atuke said the Kalenjin shot him to get land.

"I was just standing there and I got caught in the crossfire," he said, sitting in a bed with another injured man.

"SECRET POISON"

Even if Annan achieves a compromise between Kenya's bitter political rivals, ethnic tensions have taken on a life of their own in a country long seen as east Africa's most stable.

What started as a political dispute has uncorked decades-old divisions between tribal groups over land, wealth and power, dating from British colonial rule and stoked by Kenyan politicians for personal gain during 44 years of independence.

Tribal gangs have burned thousands of homes and forced out occupants perceived as not native to the region. Clouds of smoke could be seen rising from smouldering homes in the Rift Valley on Sunday. Local media said a school in Eldoret was burned.

"You have a right to reside anywhere in Kenya," shouted a bright red headline in a government statement published in the Sunday Standard. The notice warned that those who evict people from their homes would face the law.

But mobs stopping vehicles in the Rift Valley disagreed. "These Kisii, we shall kill them all," said one woman.

In an indication of gangs being organised, a white pickup delivered food and milk to armed youths in Chebilat town before they used tyres, petrol and straw to torch a medical centre.

Despite Annan's efforts, Kibaki and Odinga remain at loggerheads. Kibaki infuriated Odinga on Friday by making the provocative remark at an African Union summit in Ethiopia that he was elected by a majority of Kenyans.

"The president says we should go to court but the president is behind the court. No, we shall use these," Cheriot said, saying his arrows were "dipped in secret poison."