There are almost daily reports of new attacks
The Nigerian military has exhumed seven fresh corpses from shallow graves near the city of Jos, in the latest apparent revenge killing.
There are almost daily reports of attacks on people in rural villages and of disappearances in Jos itself.
The bodies of two local farmers were discovered earlier this week - three other people are still missing.
Clashes between rival communities - Hausa Muslims and Berom Christians - have left hundreds dead this year.
The BBC's Caroline Duffield in Lagos says tensions were high in Plateau State at the weekend - because a Christian pastor and his wife were abducted and murdered in the next door state, Bauchi.
JOS, PLATEAU STATE
Deadly riots in 2001, 2008 and 2010
City divided into Christian and Muslim areas
Divisions accentuated by system of classifying people as indigenes and settlers
Hausa-speaking Muslims living in Jos for decades are still classified as settlers
Settlers find it difficult to stand for election
Communities divided along party lines: Christians mostly back the ruling PDP; Muslims generally supporting the opposition ANPP
On Monday, aid workers found the mutilated bodies of an elderly man and a woman, Berom farmers close to Rim village, south of Jos.
They had machete wounds and acid burns.
Aid workers photographed a trail of blood - they believe it is that of three more missing villagers.
Now the military has unearthed the remains of seven people from shallow graves close to the village of Rahoss.
Our reporter says they are thought to be Hausa Muslim travellers hacked to death in a machete attack.
The killings are not thought to be directly linked but part of the hostility between local farmers and Hausa Fulani herdsman.
Farmers experience regular attacks and low-level raids and killings from Fulani herdsmen in remote areas.
Outside the city, the violence is about a struggle for farmland, and grazing rights, our reporter says.
But in Jos itself, the friction is deeply political, she says.
Violence is often sparked by settlements spilling into new land - or by tension in local government.