"We urge the government to do more to provide security and protection to civilians, especially in areas prone to attacks and where a state of emergency has been proclaimed," Ravina Shamdasani, a spokeswoman for U.N. human rights chief Navi Pillay, said in a statement Tuesday.
Shamdasani said her office was appalled by the violence in northern Nigeria states that left at least 150 people dead last weekend. Government officials said Islamic militant group Boko Haram carried out the attacks.
The spokeswoman said the Nigerian government was called on to "make sure that perpetrators of these gross human rights violations and killings are duly prosecuted and held responsible."
The U.S. State Department in November designated Boko Haram as a foreign terrorist organization.
Late January violence in northern Nigeria prompted the British Foreign and Commonwealth Office to issue a travel warning advising Britons of the "high threat from terrorism."
Nigerian President Goodluck Jonathan declared states of emergency for northern states in response to heightened Boko Haram activity last year.