This post was last updated at 11:50 a.m. ET.
Three U.S. military aircraft running evacuation flights out of South Sudan were fired upon on Saturday, leaving four service members injured, a spokesman for U.S. Africa Command said.
United States Africa Command says all four service members have been treated and are in stable condition.
The three CV-22 Ospreys were fired on while flying out of Bor, which NPR's Gregory Warner reports is not under government control.
The AP reports that once the Osprey received fire, they headed to Kampala, Uganda, and the wounded servicemen were then flown to Nairobi, Kenya, for treatment.
"South Sudan President Kiir, an ethnic Dinka, said this week that an attempted coup triggered the violence now pulsing through South Sudan. He blamed the former vice president, Machar, an ethnic Nuer. But officials have since said a fight between Dinka and Nuer members of the presidential guard triggered the initial violence late Sunday night. Machar's ouster from the country's No. 2 political position earlier this year had stoked ethnic tensions.
"The violence has killed hundreds and has world leaders worried that a full-blown civil war could ignite in South Sudan. The south fought a decades-long war with Sudan before a 2005 peace deal resulted in a 2011 referendum that saw South Sudan break away from the north, taking most of the region's oil wealth with it."
ABC News reports that the U.S. has been running evacuation missions out of the country since Monday, when two C-130 aircraft pulled 120 Americans and Western diplomats from Juba.
"The planes also carried in 45 members of the U.S. military's East Africa Response Force (EARF) to stay behind in Juba to protect the U.S. embassy and the American diplomats who remained behind," ABC reports.
Update at 11:44 a.m. ET. Stable Condition:
United States Africa Command says all four service members who were injured in the attack have been treated and are in stable condition.
A military spokesman adds that the service members were aboard three military aircraft on a State Department mission to evacuate U.S. citizens from the town of Bor.
"As the aircraft, three CV-22 Ospreys, were approaching the town they were fired on by small arms fire by unknown forces," the military said in a statement. "All three aircraft sustained damage during the engagement."