The UN office stated this in New York.
Rupert Colvile, the spokesperson for the UN Office of the High Commissioner for Human Rights (OHCHR), said this in a statement made available at the UN Head quarters in New York on Friday.
He reiterated calls on Boko Haram and other extremist groups in Nigeria to cease their “cowardly attacks” against civilians, members of government institutions, security forces and foreign nationals.
“The High Commissioner noted that members of Boko Haram, if judged to have committed systematic attacks against a civilian population on grounds such as religion or ethnicity could be found guilty of crimes against humanity.
“Deliberate acts leading to population `cleansing’ on grounds of religion or ethnicity could also amount to a crime against humanity,” Mr. Colville stressed.
In recent weeks, more than 220 people have been killed in violent clashes between military forces and the Islamist group, Boko Haram.
OHCHR has urged the Nigerian government to abide by human rights principles during security patrols.
The rights body also said it was concerned about the large number of casualties, reportedly including many civilians, and massive destruction of houses and property.
Mr. Colville urged the government to ensure that international human rights law was respected during its emergency operations.
Similarly the Secretary-General, Ban Ki-moon had said he remained very concerned about the ongoing instability in the country.
He underscored the need for all concerned to fully respect human rights and to safeguard the lives of all Nigerians.
President Goodluck Jonathan on Tuesday declared a State of Emergency in three North Eastern states most prone to Boko Haram attacks. The military has already deployed more troops including, reportedly, fighter jets to dislodge the insurgents who have been blamed for the death of hundreds of people in various violent operations across Nigeria.