The UN Mission in South Sudan says it has evidence rebel forces have murdered civilians, including children, in the key oil hub of Malakal.
South Sudan's army and rebels have traded accusations over atrocities reportedly committed during heavy fighting in Malakal, in defiance of a ceasefire signed on January 23.
A UNMISS patrol that visited Malakal on Thursday spoke with eyewitnesses who indicated "armed opposition forces targeted and killed 10 unarmed civilians at the Malakal Teaching Hospital on the basis of their ethnic background", said a UN statement issued on Friday.
The unrest in South Sudan, the world's newest nation, has left thousands dead and displaced close to 900,000 people, including tens of thousands crammed into UN bases in fear of ethnic attacks by either President Salva Kiir's Dinka tribe or his former vice president Riek Machar's Nuer tribe.
The conflict between troops loyal to Kiir and rebels backing Machar broke out in the capital Juba on December 15 amid tensions within the ruling party but quickly spread.
UNMISS staff also reported witnessing the extrajudicial killing of two children just outside the mission's compound. The gunmen were believed to be rebel-aligned youths.
"It is clear that civilians bore the brunt of much of the fighting and that gross violations of human rights were committed," the UN said.
An interim report drafted by the mission and handed to the UN Security Council details alleged human rights abuses committed by both sides between December 15 and late January. A final report is due in April.
"Large numbers of civilians were deliberately targeted and killed along ethnic lines and many more were displaced for similar reasons," the UN said, citing the interim report.
It points to Nuer killed by Sudan People's Liberation Army soldiers in Juba in the first three days of the conflict and Dinka killed in Malakal by young Nuer and deserters who left the national security forces.
