The International Committee of the Red Cross warned this week the conflict in Jonglei, the largest state in South Sudan, was spiraling out of control.
Human Rights Watch said Friday the South Sudanese military had committed serious human rights violations. The advocacy group said "thousands" of civilians were forced to flee their homes, leaving the displaced population vulnerable to ongoing ethnic conflict in the region.
Daniele Bekele, research director for African programs, said in a statement the South Sudanese government has "utterly failed" to prevent violence in the country.
"This failure, together with a spate of serious abuses by soldiers in the area, only reinforces the perception that South Sudan's leaders are taking sides in this ethnic conflict," he said in a statement from Nairobi.
The United Nations estimated at least 100,000 people were cut off from emergency humanitarian assistance because of conflict in Jonglei. U.N. Emergency Relief Coordinator Valerie Amos said she was "alarmed" by the crisis.
Human Rights Watch called on South Sudanese President Salva Kiir to publicly condemn the violence in Jonglei and order an investigation into the abuses.