At least 51 people were killed by gunmen in the early hours of Monday in Nigeria's northern Plateau state, residents and Amnesty International said, two weeks after deadly clashes in another part of the state left dozens dead.

Last week, the national emergency agency said gunmen had killed at least 52 people and displaced nearly 2,000 others over several days of attacks in Plateau, which has a history of violence between farmers and cattle herders.

On Monday, residents said 51 bodies had been recovered in the Zikke and Kimakpa villages in Plateau's Bassa district, while several more were reportedly injured.

The cause of the attack was not immediately known.

"A mass burial is currently underway. There is outrage in the land at the moment," said resident Joseph Chudu Yonkpa, who said the gunmen were cattle herders.

A police spokesperson did not immediately comment.

"No community deserves to go through such trauma, bloodshed, and destruction," said Albert Garba Samuel, spokesperson for local youth group Jere Nation Youths Development Association.

Amnesty International Nigeria said the gunmen also razed and looted homes.

"The inexcusable security lapses that enabled this horrific attack, two weeks after the killing of 52 people, must be investigated," Amnesty said in a statement.

Plateau is one of several ethnically and religiously diverse hinterland states known as Nigeria's Middle Belt, where inter-communal conflict has claimed hundreds of lives in recent years.

The violence is often painted as ethno-religious conflict between Muslim herders and mainly Christian farmers. But climate change and the reduction of grazing land through agricultural expansion are also major factors.

Reuters