Heavy gunfire has erupted in South Sudan's capital in what security sources say is fighting between rival factions of the country's military.
There were no immediate reports of casualties on Monday; the violence began overnight at a military facility in Juba.
Hilde Johnson, the U.N. special representative for South Sudan, urged everyone involved to end the fighting, and said she had been in contact with key leaders to call for calm.
The Associated Press quoted South Sudan military spokesman Philip Auger saying the army was in "full control" of the city and that the situation was not likely to deteriorate.
The U.S. Embassy in Juba expressed concern about the violence and cautioned its citizens to remain indoors.