Community leaders in Nigeria's Plateau State are appealing for calm in villages outside the city of Jos.
At least six people - women and children - were killed, cattle slaughtered and homes burned in one village this week.
In January and March this year, similar attacks prompted a spiral of rioting and killing in the region that left hundreds of people dead.
Leaders in Ranwianku are urging residents not to think of revenge.
Of those killed, one was an elderly woman unable to flee the armed gang, one was a young mother and four were small children.
Photographs of a mass grave show tiny bodies wrapped and lying side by side.
Ranwianku is a predominantly Christian settlement - eyewitnesses in the village say those that attacked spoke the Fulani language.
In Jos and surrounding areas, the two communities - Berom Christians and Hausa Fulani - continue to live uneasily together after the mass bloodshed of earlier this year.
Out in the remote villages, the tensions are not about religion or politics but about grazing rights and land ownership.
Berom Christian farmers say they regularly experience low-level harassment and killings from Fulani herdsman, who graze cattle on the land.
The Fulani community often complain of the theft or slaughter of cattle.
Damage caused to property by cattle - or disputes over the loss of cattle - is often at the root of violence between the two ethnic groups.
BBC News
