A US plane was hit by gunfire Saturday as it was evacuating people from South Sudan, said a military official in Uganda, where the plane made an emergency landing. "It was the US plane that was hit, and it landed in northern Uganda," military spokesman Paddy Ankunda said. CNN quoted Pentagon spokesman John Kirby as saying four US service members were injured when gunfire hit their aircraft as it was trying to land in Bor, the capital of South Sudan's Jonglei state, an epicentre of violence in the past week. The United States is one of several nations, including Uganda, that are evacuating citizens from the chaos emerging in South Sudan, where some military units are revolting against the central government, German Press Agency dpa reported. Kenyan President Uhuru Kenyatta has ordered the deployment of troops to South Sudan to evacuate 1,600 Kenyan citizens, most of whom are based in Jonglei, where the hostilities are strongest. African nations are working to negotiate a ceasefire in the world's newest nation, but as yet, there was no indication the talks were leading to any political deals. US Secretary of State John Kerry said he was also sending a special envoy to help with the talks.