Rape committed against victims as young as two is being used systematically as a weapon of sexual violence by both sides in South Sudan's civil war, according to United Nations officials.

"Survivors and healthcare workers told me heartbreaking stories of rape, gang rape, abduction, sexual slavery, and forced marriage," Zainab Haw Bangura, the UN's special representative on sexual violence in conflict, told reporters Monday after returning from a six-day trip to the country. "Both parties have committed crimes."

War in the world's youngest country broke out in December 2013 when forces loyal to former Vice President Riek Machar took up arms against government soldiers commanded by President Salva Kiir. The ensuing violence and rape has largely fallen along ethnic lines, perpetrated between a mostly Dinka army and predominantly Nuer rebels, many of them former government soldiers.

After taking the town of Bentiu in April, rebel fighters used a local radio station to incite the rape of Darfuri and Dinka women. At the time, a spokesperson for the UN mission in South Sudan (UNMISS) told VICE News some of the broadcasts "called on men to avenge past-gender based violence against women of their own community."

During the capture of Bentiu, hundreds of civilians were murdered, many of whom had sought shelter in a local mosque. Rebels reportedly used a church in the town of Malakal as a "rape camp" for months, despite the presence of UN peacekeepers nearby.

"We know that people were raped because of their ethnicity," said Bangura. "If people are raped because of their ethnicity it means someone has been instructed. It is a crime that is commanded."

Officials at a hospital in the capital Juba told Bangura that 74 percent of rape and sexual assault victims were under the age of 18. The youngest they treated was only 2 years old.

Bangura's office told VICE News that the details of that case could not be shared in order to protect the identity of the victim..

"Those who try to fight back against their attackers are often raped with objects instead," said Bangura. "Some victims have been raped to death."

Bangura's testimony echoed a May report published by UNMISS, which found that "all parties to the conflict have committed acts of rape and other forms of sexual violence against women of different ethnic groups."

"Forms of sexual violence used during the conflict include rape, sometimes with an object (guns or bullets), gang-rape, abduction and sexual slavery, and forced abortion," the report said. "In some instances, women's bodies were mutilated."

Civilians in South Sudan — which achieved independence from Sudan in 2011 — have grown grimly accustomed to rape carried out by various armed groups.

"Sexual violence has been a feature of the way wars have been fought in Sudan since before independence, and in South Sudan after independence," Akshaya Kumar, South Sudan and Sudan policy analyst at the Enough Project, told VICE News.

"If you look back to the 1990s, a large part of South Sudan's second civil war was fighting between various rebel factions," Kumar added. "Sexual violence featured heavily as a weapon of war, and people began to view women as legitimate targets. Women were seen as another battlefield to be conquered."

In 2012, investigators at Amnesty International identified instances of severe human rights violations, including rape, that they said had been perpetrated by government forces in Jonglei State.

Critics of the international response to the present war in South Sudan say that the humanitarian community and the UN both largely ignored simmering inter-ethnic and political tensions ahead of the violent schism that broke out last December.

"There was never any accountability for what happened in Jonglei or what happened between Dinka and Nuer factions in the 1990s, or what the government of Sudan did in the South," said Kumar.

Both sides of the conflict have effectively ignored a series of ceasefires beginning in January. The civilian toll has been particularly high, as each side abandons and retakes strategic towns — many near vital oil installations — while leaving non-combatants to fend for themselves.

Fighting has somewhat abated in recent months as the rainy season has rendered significant stretches of the country impassable. Nevertheless, UN peacekeeping chief Herve Ladsous said last month that a return to widespread violence is all but assured once the dry season begins.

At least 10,000 South Sudanese have died since last December, and an additional 1.7 millionhave fled their homes. The aid group Oxfam says that more than 2 million people already face starvation. The UN estimates that as many as 50,000 children under the age of 5 could die before the end of the year without treatment for acute malnutrition.

Overtaxed peacekeepers have been largely occupied with guarding some 100,000 displaced locals who have taken refuge at 10 UN bases across the country. Women are vulnerable to rape even at the UN camps, according to Bangura, particularly when they go to seek firewood or go to bathe. In a September report, the UN counted 215 "security incidents" that had taken place at UN protection sites, among them assault and rape.

Human rights observers have called for greater dissemination of human rights reporting in South Sudan as a means of breaking a decades-long lack of prosecution.

"The problem of impunity has to be addressed," Bangura said, but noted that referral to international justice mechanisms like the International Criminal Court was up to the Security Council.

An African Union commission of inquiry is expected to release a report on the conflict later this month that is believed to include documented incidents of rape. A spokesperson for Bangura told VICE News that the commission had not yet shared their findings with her.

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