Kenyan police have arrested seven people following last week's deadly attack on the northern village of Turbi, which sparked retaliatory acts.
The deadly attack on villagers left scores of people dead
Police have identified two of them as the ringleaders in the killings.
The number of people who fled their homes and are seeking refuge in larger towns, mainly Marsabit, has increased to 9,000, the Kenyan Red Cross says.
The Borana community has been blamed for the raid on Turbi, in which dozens were killed, including 22 children.
"The situation is still volatile and tense with possible escalation of the conflict," Farid Abdul Kadir, the Red Cross head of disaster response, told the AFP news agency.
The feud between Boranas and Gabras is a long-standing one, mainly based on disputes over access to water and pastures.
But last week's attack is considered to be the most brutal one in the country's post-colonial era.
The Red Cross on Friday appealed for 53.9m shillings ($709,000; £405,000) but has so far only received some 6.8m.
Dozens of those hurt in the attack, in which children were shot at and hacked to death with machetes while on their way to school, are still in hospital.
Kenyan President Mwai Kibaki has been accused of reacting too slowly or inappropriately to the violence, as well as to a case of mass poisoning involving illegally-produced alcohol in which 50 people died last month.
In an official statement, the presidential press service said his response had been "timely" and his actions had been misreported by the media.
Hundreds of livestock have been stolen in the raids and Kenyan authorities are determined to track the culprits down before they reach the border with Ethiopia.