Fresh fighting erupted in South Sudan's capital on Tuesday, a day after President Salva Kiir said his government had stopped an attempted coup.
Witnesses in the capital, Juba, say sporadic gunfire could be heard throughout the day as soldiers patrolled the streets.
Government officials say the violence has killed at least 26 people, while a U.N. radio station says doctors at a local hospital have treated more than 100 people for gunshot wounds.
On Monday, President Kiir said the clashes began when forces loyal to his former vice president, Riek Machar, attacked an army headquarters.
The government said Tuesday that 10 people have been arrested in Juba for their alleged roles in the coup plot. It said Machar and four other suspects are still at large.
Machar, a critic of Mr. Kiir, was fired by the president during a Cabinet reshuffle in July. He has said he will run for president in 2015.
Government security forces have imposed a nighttime curfew in Juba and are searching door-to-door for those blamed for the fighting.
The United Nations Mission in South Sudan estimates 10,000 civilians have sought protection at two of its compounds in Juba, with 39 people receiving medical treatment.
Hilde Johnson, the U.N. special representative for South Sudan, has urged South Sudan's leaders to "refrain from any action that fuels ethnic tensions" and makes the violence worse.
The U.S. Embassy in Juba remained closed Tuesday and reported that most cellular telephone service in the city was not working.
The U.S. Special Envoy to Sudan and South Sudan, Donald Booth, told VOA on Monday that the United States is very concerned about the developments. He said the United States cannot yet confirm a coup attempt and is trying to learn what sparked the violence.
"The situation remains a bit confused. The embassy in Juba has not been able to get out much due to the fighting around town. Right now they are sheltering in place until they feel it's safe to move around the city."
U.N. Secretary-General Ban Ki-moon said he is deeply concerned by the fighting and what he said was "the risk of targeted violence against certain communities." He said the government must guarantee the security of all civilians regardless of which community they come from.