At least 500 people were killed on Sunday in communal clashes near Nigeria's central city of Jos, a state governor's advisor told AFP on Monday, revising a previous toll of around 100 dead.
"We have been able to make 95 arrests but at the same time over 500 people have been killed in this heinous act... by Fulani herdsmen," Dan Manjang said in a telephone interview.
Nigeria's central Plateau State was also quoted on state radio saying 500 people had been massacred in a night raid on three villages on the fringes of Jos.
Witnesses, reporters and local rights activists put the figure at slightly over 200.
Shamaki Gad Peter, head of the League for Human Rights in Jos, told AFP: "By our latest count there are 202 bodies".
Shehu Sani, another rights activist spoke of 250 people killed.
"So far we understand there are about 200 people dead in the three villages," a resident of Dogo Nahawa, Frank Tatgun said.
He reported no clashes overnight Monday amid tight security after authorities put the area under a red security alert and deployed troop.
The attacks blamed on mainly Muslim nomadic cattle rearers, targeted the local Berom ethnic group, which is predominantly Christian.