The United Nations has launched a probe of a hotel attack in South Sudan in which soldiers raped women and assaulted aid workers while UN peacekeepers allegedly failed to act

Civil war broke out in South Sudan in December 2013, when President Salva Kiir accused his former deputy Riek Machar of plotting a coup. The fighting has split the country along ethnic lines and driven it to the brink of collapse.

A peace deal signed between the government and rebels almost a year ago has so far failed to end the conflict. And last month, Juba was rocked by several days of heavy fighting between Kiir's forces and those loyal to Machar.

The abuses now being probed by the UN -- specifically, a July 11 attack on the Hotel Terrain in the capital Juba --took place during these days of fighting.

Secretary General Ban Ki-moon said late on Tuesday that he was 'concerned about allegations that UNMISS (United Nations Mission in South Sudan) did not respond appropriately to prevent this and other grave cases of sexual violence committed in Juba'.

He was referring to the UN peacekeeping mission in South Sudan, called UNMISS.

Ban said that in the July 11 incident one person was killed and several civilians were raped and beaten by men in uniform.