A displaced family sits with their belongings after seeking refuge at the compound of the United Nations Mission in South Sudan. South Sudan, the world's newest country, is threatened by rapidly escalating ethnic violence.

Two US military aircraft responding to the outbreak of violence in South Sudan were hit by incoming fire, wounding three US service member, officials say.

The officials said the aircraft were heading to Bor, the capital of the state of Jonglei and scene of some of the nation's worst violence over the last week.

One of the wounded service members was reported to be in critical condition. Officials said after the aircraft took incoming fire, they turned around and headed to Kampala, Uganda. From there the service members flew on to Nairobi, Kenya for medical treatment.

PA Media