The UN has launched an urgent investigation following claims that its peacekeepers in South Sudan turned a blind eye to a brutal attack on foreign aid workers in which several women were raped and beaten.

On July 11, South Sudanese troops who had just won a battle in the capital of Juba went on a nearly four-hour rampage through a residential compound popular with foreigners, in one of the worst targeted attacks on aid workers in South Sudan's three-year civil war.

They shot dead a local journalist while forcing the foreigners to watch, raped several foreign women, singled out Americans, beat and robbed people and carried out mock executions. For hours throughout the assault, the U.N. peacekeeping force stationed less than a mile away refused to respond to desperate calls for help.

Neither did embassies, including the U.S. Embassy.

"They were very excited, very drunk, under the influence of something, almost a mad state, walking around shooting off rounds inside the rooms," one American said.