A bloc of East African nations has accused South Sudan's army of committing serious human rights violations in an ongoing offensive against rebels.
Friday's statement from IGAD - the Intergovernmental Authority on Development - said mediators have received credible reports of "violence targeting civilians, grave human rights abuses and destruction of villages" during an offensive that began in Unity State and spread to Jonglei and Upper Nile States.
The statement also said government forces have denied freedom of movement to IGAD monitors in the Unity State capital, Bentiu, since the offensive began April 27.
It said the acts add up to a "significant violation" of a cessation-of-hostilities agreement the government and rebels signed last year.
There was no immediate response from the South Sudanese government.
The United Nations and international aid agencies have warned about a growing humanitarian crisis in Unity State.
Earlier this week, the U.N. said 300,000 people in the state have lost access to "life-saving aid" after fighting forced relief groups to withdraw from the town of Leer. Those groups include the International Committee of the Red Cross and Doctors Without Borders, which runs a hospital in the town.
The U.N. humanitarian coordinator for South Sudan, Toby Lanzer, warned the violence comes at a time of low food stocks and could disrupt the planting season.
Government forces backing President Salva Kiir have been fighting rebels who support former vice president Riek Machar for the past 17 months.
On Thursday, the head of the U.N. mission in South Sudan, Ellen Loej, said more than 2 million South Sudanese are displaced, including 1.5 million internally and 500,000 in neighboring countries.