South Sudan's President Salva Kiir says the army foiled an overnight coup attempt by forces loyal to his former vice president.
Mr. Kiir told reporters Monday that the government is in "full control" of the security situation in the capital, Juba, after an attack at the army headquarters.
He said residents should remain calm but declared a nighttime curfew for the city until further notice. The government and the U.S. embassy both reported "sporadic gunfire" in parts of the capital Monday afternoon.
President Kiir blamed the alleged coup attempt on troops allied with Riek Machar, a political rival whom he fired as vice president in July.
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 U.N. Mission in South Sudan said in a statement that hundreds of civilians have sought refuge at its compound, and denied "any suggestion" that it is harboring political or military figures.
In a statement, the U.S. embassy also said that "no political or military figures" had taken refuge within its walls.