Scores of people are thought to have been killed in clashes between pastoralists from the surrounding hills and villagers close to the central Nigerian city of Jos.
Police sources on Sunday put the number of dead at just eight, but witnesses reported many more bodies, with one estimate rising to up to 200 people.
Some of the bodies were reported to be charred and scarred by machete blows and the AFP news agency reported there were many children among the dead.
Yvonne Ndege, Al Jazeera's correspondent in Abuja, said: "There is conflicting information about the number of people who may have been killed.
"Police are saying about eight people have been killed but I have spoken to a number of people in Jos who said the number is higher."
The Associated Press news agency quoted witnesses saying 200 people were killed in the violence.
Goodluck Jonathan, Nigeria's acting president, put security forces on red alert, ordering them to hunt down those behind the violence.
"The acting president has placed all the security forces in the plateau and neighbouring states on red alert so as to stem any cross-border dimensions to this latest conflict," a statement from Jonathan's office said.
Witnesses said that the pastoralists staged an overnight raid in the village of Dogo Nahawa, firing into the air and then attacking those who came out of their houses.
"They came around three o'clock in the morning and they started shooting into the air," Peter Jang, a Dogo Nahawa resident, said.
"The shooting was just meant to bring people from their houses and then when people came out they started cutting them with machetes," he said.
Ndege reported: "A senior police chief said the perpetrators of this attack came in from Bauchi state. [He said] the fighting exploded between herdsmen from Bauchi and villagers.
"The Red Cross, is reporting that as a consequence of this violence at least 5-600 people are leaving the area in fear of their lives."
Nearby Jo, which lies at the at the crossroads of Nigeria's Muslim north and predominantly Christian south, has been the scene of sectarian violence before.
Hundreds of people were killed in four-days of violence in January.
Patrick Wilmot, a sociologist and African affairs analyst based in London, told Al Jazeera that the problems in the area of Jos stem from a lack of economic development.
"People from all over Nigeria came and settled in the area [of Joss]. There was hardly any trouble in the area 15 or 20 years ago, but [since] then the population has increased tremendously, [but] the resources have not increased.
"There are hardly any industry in the town. There is only one large factory. most of the economy is based o commerce and farming and as a result of huge unemployment the people have become very attached to their religious and ethnic identities.
"The political leaders are irresponsible, they manipulate these fears of religious and ethnic differences and as a result its a kind of tinderbox."