KAMPALA, Uganda (AP) — A crew member was killed and two others were injured when a United Nations helicopter on an evacuation mission in a remote part of South Sudan was attacked on Friday, the U.N. mission in South Sudan said, as violence escalated in fighting that threatens a fragile peace deal between the country's top two leaders.

The aircraft came under fire as it tried to rescue wounded soldiers, the United Nations said. The attack came amid fears that a critical power-sharing deal was at risk of collapse, risking all-out civil war.

Plenty pipo don die for South Sudan afta one attempt by di UN to evacuate members of di national army come under fire, di UN confam. One crew member die wen dem shoot at one UN helicopter, statement from dia mission for South Sudan,

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 the Upper Nile state.