A U.S. military aircraft came under fire Saturday during a reported evacuation mission in South Sudan, leaving four U.S. service members wounded, one critically.

"The aircraft diverted to an airfield outside the country and aborted the mission," reads a statement from the U.S. military's Africa Command.

The aircraft fell under attack as it headed to Bor, the capital of the state of Jonglei and ground zero of an escalating conflict between South Sudan's military and defected armed forces.

South Sudan's military spokesperson said renegade troops who had seized control of the region were responsible for the attacks, according to Al Jazeera America.

The injuries follow the killing of three UN peacekeepers from India earlier this week and over 500 civilian deaths, with many warning that oil-rich South Sudan stands on the verge of a deadly civil war as violence spreads.

Tens of thousands of civilians are fleeing the violence and reportedly crowding into UN peacekeeping bases.

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