"Over the last four days close to 75 Kenyans have died. Is it worth it, and what for?" Kenya Red Cross chief Abbas Gullet said.
"In the 21st century, we can't have Kenyans killing one another -- especially these pastoralist communities who come from a very marginalised environment," he said.
The violence started in northern Kenya's Turkana and East Pokot districts, and clashes have also been reported in the nearby districts of Marsabit, Samburu and Baringo.
In the worst fighting, gunmen from the ethnic Turkana people are suspected of launching an attack on Monday against an ethnic Pokot village along the Turkana-East Pokot district border, an area where there are frequent deadly conflicts between the two communities.
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According to a county official, the violence started after an attack by Pokot warriors on a Turkana village in which 100 goats were stolen.
Red Cross teams are supporting some 350 families who have fled days of clashes.
"These communities, through their leadership, should come together with common sense and start talking as opposed to cattle rustling," Gullet said.
Retaliatory cattle raids as well as armed disputes over water and pasture are common among Kenya's northern pastoralists.