The report accused both rebel and government armies in South Sudan with abuses.
Taban Deng Gai, the rebel forces' chief negotiator at peace talks in Addis Ababa, Ethiopia, said his army is "not denying innocent persons lost life in Malakai, Bentiu or Bor," referring to the state capitals of Upper Nile, Unity and Jonglei, respectively, the Sudan Tribune reported Monday..
He added if any rebel soldiers were implicated in war crimes, they "shall face the law."
Human Rights Watch researchers found: "Armed forces from both sides have extensively looted and destroyed civilian property ... and carried out extrajudicial executions, based on ethnicity."
Fighting broke out in December, and in following days the government army targeted people from the Nuer ethnic group, the tribe of former Vice President Riek Machar. The government accuses Machar of attempting to overthrow President Salva Kiir.