Last flight for Britons in South Sudan coup: Foreign Office urges residents to flee on UK's third and final evacuation aircraft Newly-formed African state was hit by a coup attempt in the capital Juba UN estimates up to 500 people have been killed in fight between factions Three U.S. rescue planes hit by incoming fire, leaving four wounded Britons in South Sudan are being urged to flee the troubled country on the UKâ€™s third and final evacuation flight. The Foreign Office said a plane was being sent to the capital, Juba, today and warned that the British government would struggle to help anyone who chose to stay behind. Fighting has spread through the newly formed African state, which gained its independence from Sudan in 2011, after a coup attempt in the capital last weekend. Flight: Britons have been urged to evacuate South Sudan today on what will be the final rescue flight. Pictured: U.S. soldiers of the East Africa Response Force (EARF) are deployed in the capital on December 18 Factions: A Sudan People's Liberation Army soldier in the capital Juba on Saturday British military transport planes have been used to evacuate two groups of UK nationals over recent days. Three U.S. rescue planes were hit by incoming fire, leaving four American service personnel wounded. The UN has estimated that up to 500 people have been killed in fighting between rival factions following a coup attempt against President Salva Kiir by troops loyal to former vice-president Riek Machar. A Foreign Office spokesman said: 'Due to the continued violence in South Sudan, the Foreign and Commonwealth Office (FCO) is planning to send a third and final plane to assist any remaining British nationals to leave. Fire: A U.S. CV-22 Osprey aircraft similar to three which were hit in Bor in remote South Sudan Danger: British citizens have been warned the government may no longer be able to support them The FCO is planning to provide a charter flight to depart from Juba to Dubai during the afternoon of Monday, December 23. Following the assisted departure of British nationals earlier this week on military flights, this will be the final flight provided by the FCO for British nationals to leave South Sudan.