Fresh ethnic clashes in western Kenya's Rift Valley Sunday killed at least 20 people and injured scores of others.

Witnesses say the violence has spread to the previously quiet tourist town of Naivasha, where people were hacked to death, shot with arrows or burned to death in their homes.

The violence between rival tribes continued in Naivasha despite the heightened presence of soldiers and police.

Since the controversial presidential elections a month ago, the fighting killed nearly 800 people and displaced more than 250,000 others.

Kenyan President Mwai Kibaki with former UN Secretary-General, Kofi Annan, at State House Nairobi,26 Jan 2008

The violence complicates the mission of former U.N. Secretary-General Kofi Annan, who is trying to bring together President Mwai Kibaki and opposition leader Raila Odinga.

Annan said after visiting the region that the election dispute had resulted in "gross and systematic" human rights abuses. He met with Odinga in Nairobi Sunday.

Odinga accuses Mr. Kibaki of rigging the December 27 vote. Most of the violence is between Mr. Odinga's Luo tribe and the president's Kikuyu tribe.

On Thursday, Annan brought President Kibaki and Mr. Odinga together for their first face-to-face discussions since the disputed election. Both sides later accused the other of seeking to undermine the talks.

Some information for this report was provided by AFP and AP.