The UN human rights chief said Thursday he was "deeply alarmed" by the string of attacks on villages in central Nigeria which left nearly 200 dead, according to local authorities.
Armed groups launched attacks between Saturday evening and Tuesday morning in Nigeria's Plateau State, a region plagued for several years by religious and ethnic tensions.
The region is on the dividing line between Nigeria's mostly Muslim north and mainly Christian south.
"I am deeply alarmed by the series of attacks by gunmen on multiple rural communities in Plateau State," UN rights chief Volker Turk said in a statement.
"I call on the Nigerian authorities to investigate this incident promptly, thoroughly and independently, consistent with international human rights law, and to hold those responsible to account in fair trials.
"The cycle of impunity fuelling recurrent violence must be urgently broken. The government should also take meaningful steps to address the underlying root causes and to ensure non-recurrence of this devastating violence."
Northwest and central Nigeria have been long terrorised by bandit militias operating from bases deep in forests and raiding villages to loot and kidnap residents for ransom.
Competition for natural resources between nomadic herders and farmers, intensified by rapid population growth and climate pressures, has also exacerbated social tensions and sparked violence.
A jihadist conflict has raged in northeastern Nigeria since 2009, killing tens of thousands of people and displacing around two million, as Boko Haram battles for supremacy with rivals linked to the Islamic State group.
Nigerian President Bola Ahmed Tinubu has made tackling insecurity a priority since coming to office in May, as he seeks to encourage foreign investment in Africa's most populous country.
