Fighters allied to the government in South Sudan, seem to have been "allowed to rape women and girls in lieu of wages", according to a UN report.

Between April and September last year the UN Human Rights Office recorded 1,300 reports of rape in the South Sudanese state of Unity.

One woman watched her 15 year old daughter being raped by 10 soldiers while others were abducted and held in 'sexual slavery' for soldiers in barracks.

The report said that the prevalence of rape, "suggests its use in the conflict has become an acceptable practice" and women and girls "were considered a commodity and were taken along with civilian property as the soldiers moved through the villages."

The UN said children have "borne the brunt of the violence" and it received reports of 702 children affected by incidents of sexual violence since the start of the conflict, with some victims of gang rape as young as nine years old.

The UN also found a range of other human rights violations by government soldiers and militia groups including "systematic violence against civilians".

Some people told the UN that civilians, including children and the disabled, were murdered by being burned alive,suffocated in containers and hanged from trees.

The UN report adds that all parties to the conflict have conducted, "attacks against civilians, rape and other crimes of sexual violence, arbitrary arrest and detention, abduction and deprivation of liberty, disappearance, including enforced disappearance, and attacks on UN personnel and peacekeeping facilities".

More than two million South Sudanese have been displaced and tens of thousands killed since violence erupted in South Sudan in December 2013.

Despite a peace agreement signed in August last year the UN said the warring factions are yet to establish a promised Transitional Government of National Unity.