Amnesty International says South Sudanese security forces have committed "shocking" human rights violations, while carrying out a campaign to disarm civilians in Jonglei state.
The group said in a report Wednesday the violations by members of the police and army include torture, shootings and sexual violence.
The report is based on interviews with people in Pibor County. In August,
Human Rights Watch and the United Nations Mission in South Sudan alleged similar abuses in the same area.
Officials dismissed the earlier reports as "politicized" and "inflammatory," saying the allegations had been overblown.
Amnesty International on Wednesday called for South Sudan to conduct independent and impartial investigations into the alleged abuses. It also urged the U.N. mission to increase its efforts to protect civilians.
The army launched the disarmament campaign earlier this year after a wave of ethnic violence between the Lou Nuer and Murle tribes in Jonglei.
The United Nations estimated that more than 600 people died after thousands of armed Lou Nuer youth, along with some of the dominant Dinka tribe, rampaged through villages in Pibor County. Around 300 others were killed in revenge attacks.