Eighty civilians, including 57 children, were killed in just one county in war-torn Unity state between Oct. 4 and 22, according to a group of humanitarian organizations monitoring civilian casualties in South Sudan.
Twenty-nine of the children drowned after running into swamps to hide from attacks in Leer County. There were reports of widespread sexual violence, including more than 50 rape cases, said the Protection Cluster, representing 60 local and international organizations.
Kuong Kuony, the rebels' commissioner for Leer County, accused government troops of launching attacks on rebel positions, burning civilian houses, and looting livestock.
South Sudan's military spokesman, Col. Philip Aguer, said Saturday that he had no reports of fighting in Leer County.
The United Nations and human rights groups have documented widespread abuses against civilians in the country, including rapes and killings by government soldiers and their militia, in Unity state this year.
Fighting persists despite a peace deal signed in August.
The latest incidents took place following a brief takeover of Leer town by rebel forces on Oct. 2. Government forces pushed the rebels out later that day, the Protection Cluster said. The government forces then attacked numerous locations across the county, chasing civilians into swamps, according to many survivors who spoke to the Associated Press in Unity state during and after the attacks.
"As a result of this new wave of violence, it is estimated that nearly 1,200 children are unaccompanied and separated in southern and central Unity State," the Protection Cluster said.
South Sudan has been at war since December 2013 as government forces loyal to President Salva Kiir, an ethnic Dinka, battle rebels led by his former deputy, Riek Machar, a Nuer. The fighting has often been along ethnic lines.
On Thursday, the U.N. warned in a report that over 30,000 people in South Sudan's war zone face death by starvation and that tens of thousands more are on the brink of famine.