Britain says it is withdrawing some embassy staff from South Sudan after fighting in what the government calls an attempted coup spread to areas beyond the country's capital.
The U.N. estimates days of fighting in South Sudan have killed up to 500 people. The British Foreign Office says its embassy in the South Sudanese capital, Juba, will remain open while some staff is withdrawn temporarily.
The U.N. mission in South Sudan reported heavy fighting in the city of Bor. The mission said more than 1,000 civilians have sought shelter at its compound in Bor, about 150 kilometers north of Juba.
There was also fighting overnight at a military base in Torit, southeast of the capital.
The Sudan People's Liberation Army has called all soldiers to report to their general headquarters.
South Sudanese officials have urged residents to return to their homes following the deadly clashes.
Late Tuesday, the U.N. Security Council expressed concern about the risk of violence targeting certain groups and called for South Sudan's government to hold talks with its opponents.
U.S. Secretary of State John Kerry says the people of South Sudan have sacrificed too much for their country to return to violence.
"Political differences need to be resolved by peaceful and democratic means and those have been hard fought for. The government should respect the rule of law and the people of South Sudan should be able to realize their full potential in peace," said Kerry.
President Salva Kiir blamed the coup attempt on forces loyal to his former vice president, Riek Machar, whom he fired in July.
Observers have raised concerns a rift between Machar, from the Nuer ethnic group, and Kiir, a Dinka, could fuel tribal violence in South Sudan.
South Sudan's government said 10 people have been arrested for their alleged roles in the coup attempt, while Machar remains at large.
Government security forces have imposed a nighttime curfew in Juba and are searching door-to-door for those blamed for the fighting.
The U.S. State Department has ordered the departure of all non-essential personnel from South Sudan and is urging all Americans in the country to leave immediately.