Kenyan officials say 13 people have been killed and four wounded since Sunday in the volatile Rift Valley county of Baringo, where a drought has increased cattle rustling.
The violence occurred despite a police operation to disarm the herding communities.
Kenya Red Cross Secretary-General Abbas Gullet said Wednesday that four children and seven women are among the dead.
Police spokesman George Kinoti says Illchamus herders attacked Pokot herders on Monday in Partololo village, killing two people and stealing 30 cattle. That triggered a cycle of revenge attacks by both communities on Tuesday.
The fighting was sparked by the killing of three people, including a politician, in early February.
Livestock thefts by nomadic tribes in the semiarid region are common.
Kenya’s government has declared the current drought a national disaster.