"We condemn in the strongest terms Mr. Ajak's continued detention and urge the South Sudanese authorities to release him immediately," a group of United Nations experts have said.
Since his arrest seven days ago, Peter Biar Ajak has not received formal charges or any answer as to why he is being detained by South Sudan officials.
Peter Biar Ajak has been detained because he's a threat to South Sudan's corrupt regime, his friends and family say.
Previous agreements have failed to bring permanent peace in the world's youngest country.
Around 535 million children—a quarter of the world's child population—live in fragile states, affected by natural disasters, epidemics and other emergencies.
The State Department has classified these 11 nations as "Do not travel."
The long list includes a Haitian immigrant who has helped save infants from a deadly disease.
The U.S. backed the country in its independence struggle. Now, it is needed again.
A U.S. intelligence agent is assisting with the prosecution of suspects accused of killing a South Sudanese aid worker and raping his foreign colleagues.
Experts know from the 2014 epidemic that when the deadly virus crosses borders it sticks around for awhile.
Soldiers killed 114 civilians, raped countless women and attacked funerals in a recent offensive, according to a U.N. report.
Almost half the population face food shortages and 100,000 people are at risk of immediate starvation in South Sudan.
At least 82 aid workers have been killed since 2013 in South Sudan, the U.N. says.
Some 16 million people in the region are in urgent need of food, water and healthcare.
Nearly half the population will not have a reliable food source by summer.