The president of the Central African Republic fled the country for Cameroon after rebels overran the capital of the impoverished nation long racked by rebellions.
South Africa said Monday that 13 of its soldiers were killed in fighting with rebels, prompting criticism about why its forces had intervened in such a volatile conflict.
Ousted President Francois Bozize sought "temporary" refuge on its territory, the Cameroonian government confirmed Monday.
The Central African Republic's new leadership appeared fragmented, with a split emerging in the rebel coalition that seized the capital.
The African Union on Monday imposed a travel ban and an asset freeze on seven leaders of the rebel coalition, known as Seleka, and said their advance had undermined prospects for a lasting solution to the crisis in the landlocked country. It urged African states to deny "any sanctuary and cooperation" to the rebel chiefs.
The United States is "deeply concerned about a serious deterioration in the security situation" in the Central African Republic, State Department spokeswoman Victoria Nuland said in a statement Sunday.
"We urgently call on the Seleka leadership which has taken control of Bangui to establish law and order in the city and to restore basic services of electricity and water," the statement said.
The rebel groups making up the Seleka alliance agreed they wanted Bozize out. Some of the rebels complained of broken promises of government jobs and other benefits. Others cited the deep impoverishment of the country's distant north despite the Central African Republic's considerable wealth of gold, diamonds, timber and uranium.
Africa has a history fraught with foreign military missions, whether for humanitarian or political purposes, or some combination of the two, in times of conflict. The central part of the continent, repeatedly buffeted by interlocking rebellions, is particularly treacherous for countries with an activist foreign policy.
In addition to the South African troop deaths, another 27 soldiers were wounded.
"I think South Africa realized right from the beginning that there will be casualties," said Johan Potgieter, a researcher at the Institute for Security Studies, in Pretoria, the South African capital. "If you want to be in peacekeeping, and you don't want body bags, you should get out of there."
South Africa's losses point to the challenges that the country faces as it tries to project continental leadership amid questions about the adequacy of its resources and the clarity of political direction from Pretoria. It has participated in peacekeeping in regions including Burundi and Darfur in Sudan.
South African troops served as trainers for the national army in the Central African Republic. But more troops were sent to protect those trainers as security deteriorated, and critics questioned the collaboration with Bozize, who came to power in a rebellion a decade ago and whose commitment to past peace deals was in doubt.
This week was meant to be triumphant for South Africa, which will host Brazil, Russia, India and China at the "BRICS" summit.