The United Nations said the incident, which could deal a blow to an already fragile peace process, was "utterly abhorrent" and a possible war crime.

One crew member died when a UN helicopter was shot at, a statement from its mission in South Sudan, Unmiss, said. It added that an injured South Sudanese general and several other troops were also killed during the evacuation attempt in Upper Nile state.

NAIROBI - A United Nations helicopter attempting to evacuate South Sudanese troops came under fire in the northern town of Nasir on Friday, the U.N. mission there said, resulting in the death of a crew member and several soldiers including a general.

A UN helicopter has been shot at in South Sudan with deaths recorded. The head of the UN Mission in South Sudan, said the attack may constitute a war crime.