FACTBOX: Facts about Kenyan tribes

(Reuters) - Kenyan police battled on Saturday to stop clashes between tribal gangs wielding machetes, spears and bows and arrows that have killed at least 27 people in the western town of Nakuru since Thursday.

What began as a political stand-off evolved into a settling of scores between rival tribes in the east African nation, once one of the continent's most promising economies, whose peaceful image has been shattered by the bloodshed.

Here are some facts about its tribal communities:

* Kenya's 36 million people are split into more than 40 different ethnic groups, each with its own strong identity, a variety of cultural traditions, and separate tongues.

* The main groups are -- Kikuyu (22 percent); Luhya (14 percent); Luo (13 percent); Kalenjin (12 percent); Kamba (11 percent), according to government statistics.

* President Mwai Kibaki is a Kikuyu. His group comes mainly from the central highlands, wields strong economic power and is solidly behind him for the election.

* Opposition leader Raila Odinga is a Luo, from western Kenya near Lake Victoria on the border with Uganda. Odinga's Nairobi constituency, Langata, includes one of Africa's largest slums where a large Luo population is fanatically behind him.

* Former President Daniel arap Moi comes from the Kalenjin group that has produced most of Kenya's famous long-distance runners.

* The Maasai, Kenya's best-known tribe and favorite on tourism posters, believe their god gave them all the cattle on earth and were entirely dependent on cattle alone for centuries. Many still live on just milk and fresh blood.

* Kenya had been lauded internationally for remaining at peace since independence in 1963, while most of its neighbors in the region experienced war and chaos. But it was often criticized too for failing to tackle ingrained tribalism, compared with neighboring Tanzania, where founding President Julius Nyerere is credited with uniting the whole country against it.

* Ethnic flare-ups are common in Kenya, especially around elections. The worst incidents took place in 1992 when 1,500 people were killed in tribally tinged land clashes in the Rift Valley region. Five years later, 200 were killed, mainly in fighting in the coastal town of Mombasa.

(Reporting by Helen Nyambura; editing by Andrew Dobbie)