The U.N. Security Council has condemned fighting in two northern states in South Sudan and the repeated violations of a cease-fire agreement the government and rebels signed early last year.
In a statement late Sunday, the council said a government military offensive in Unity State caused large-scale violence that has forced 100,000 people from their homes and halted aid delivery to civilians in the area.
The council also blamed the rebels for launching an attack on the town of Malakal in Upper Nile state.
A bloc of East African nations that has been trying to mediate the conflict between President Salva Kiir's government and rebels backing former Vice President Riek Machar said it was "deeply frustrated" by the rebel violence in Malakal. The Intergovernmental Authority on Development urged both sides to follow through on their agreement and find a peaceful end to the crisis.
The government has resisted accusations that its forces violated the cease-fire agreement, arguing instead that soldiers acted in self-defense.
On Friday, the Ministry of Foreign Affairs summoned Michael McCarthy, the U.S. charge d'affaires in South Sudan, to discuss his statement in a radio interview last week saying both sides violated the cessation of hostilities in Unity state.
In a separate interview Friday, McCarthy told Radio Miraya that self-defense is permitted, but that the size and scope of what is in "credible reports" about the latest violence has the United States concerned. He said there is a large number of newly displaced people and repeated stories of entire villages being destroyed.
He called for the need to investigate what has happened and for the violence to stop.
"There's no military solution to this problem, so why keep fighting?" McCarthy said. "Let's silence the guns."