The rights group said Friday at least 40 separate villages in northeastern Nigeria have been attacked this year by Boko Haram, which has ties to al-Qaida.
Daniel Bekele, director of African programs at Human Rights Watch, said thousands of people were forced to flee their homes to neighboring Cameroon, Chad and Niger to escape Boko Haram.
"The horrific attacks by Boko Haram are having a devastating impact on northern Nigerians," he said in a statement
U.N. High Commissioner for Human Rights Navi Pillay arrived Friday in Abuja to assess the situation first hand. She said around 500,000 people are displaced in Nigeria by attacks from Boko Haram, which she said "have grown increasingly monstrous."
Pillay said the government has no choice but to respond with force, but should do so with the understanding that military action could heighten the risk for civilians.
She said, however, the crisis was no longer an internal matter because of the threats to neighboring countries.
"I call on states within the region to enhance their collaboration with Nigeria," she said in a statement.