At least 48 people are reported to have been killed in clashes over grazing land pasture between pastoral and farming communities in southeast Kenya.
Joseph Kavoo, Tana river district police chief, said Wednesday's fighting saw people burnt in their houses, hacked to death, or shot with arrows.
"They [attackers] were armed with crude weapons: machetes, bows and arrows and spears. Some had guns. As a result we have lost 31 women, 11 children and six men, all totalling to 48. Sixty cattle were also killed," Robert Kitur, the deputy police chief of the coastal region, told Reuters news agency by telephone.
Wednesday's clashes in the Reketa area of Tarassa, 300km from the capital Nairobi, mark the worst single attack since deadly post-election violence four years ago, police said.
The two communities have clashed before over the use of land and water resources, but the scale and intensity of the killings were unprecedented.
Al Jazeera's Peter Greste, reporting from Nairobi, said the attack took place in a region with a "very complicated mix of ethnicity, politics, land and resource" issues.
Said Mgeni, an area resident, told the Associated Press news agency that the attacks began at dawn when a group of about 200 people belonging to the farming Pokomo ethnic group raided a village in the Riketa area and torched all the houses belonging to the Orma, a pastoralist community.
Cattle rustling and clashes over grazing and farming land and water are relatively common among pastoralist communities in the arid patches of east Africa and often escalate into revenge attacks.
Last week the Orma attacked the Pokomo.
In a separate development, two German tourists and two pilots were killed when their aircraft crashed on Wednesday in Kenya's renowned Maasai Mara national park, with at least three other tourists badly injured, police said.
"Four people died on the spot, while three others were seriously wounded," Peterson Maelo, the local police chief, said.
A total of five Germans, four Americans and two Czechs were reported on board the aircraft.
The pilots' nationalities were not known.