(Removes reference to political head of U.N. mission resigning over the incident.)

South Sudanese Rebecca Chuol Ungdeng, poses for a photograph during a Reuters interview in Uganda's capital Kampala in this picture taken May 4, 2017, with a portrait of her and her late husband John Gatluak, a South Sudanese aid worker who was killed by government soldiers during the attack on the Terrain hotel compound in Juba, South Sudan on July 11, 2016. REUTERS/Stringer

KAMPALA (Reuters) - South Sudanese soldiers accused of raping at least five foreign aid workers and killing their local colleague last year are due to stand trial in a military court on Tuesday, a key test of the government’s ability to prosecute war crimes.

Prosecutor Abubaker Mohammed, an army colonel, told Reuters that between 15 to 20 government soldiers face charges including murder, rape and looting during the attack on the Terrain hotel in the capital Juba on July 11, 2016.

U.N. investigators and rights group have frequently accused both the army and rebels of murder, torture and rape since the civil war began in 2013, and say the crimes almost always go unpunished.

“We want to eliminate these crimes within the army,” Mohammed said, adding he would examine the responsibility of senior officers.

“The commander is always responsible for the actions of the soldiers,” he said. “But ... sometimes a soldier can go and commit an offense without the knowledge of the commander.”

The attack, one of the worst on foreign aid workers in South Sudan’s civil war, took place as President Salva Kiir’s government troops won a three-day battle in Juba over opposition forces loyal to former Vice President Riek Machar.

The three-year conflict has fractured the country along ethnic lines -- Kiir is an ethnic Dinka, Machar is a Nuer -- and forced a quarter of the 12 million-strong population to flee their homes.

During the hours-long attack on the hotel compound, victims phoned U.N. peacekeepers stationed a mile away and begged for help, but none came. The military head of the peacekeeping mission was fired and the political head resigned over the incident.

SURVIVORS SPEAK OUT

Murderers face a minimum of 10 years in jail with a fine paid to the victim’s family, or a maximum of the death penalty, Mohammed said. Rapists face up to 14 years.

Rebecca Chuol Ungdeng, whose aid worker husband John Gatluak was killed in the attack, said she feared returning for the trial.

“Why was he killed while he is not a soldier?” she said from exile in Uganda. “He has no enmity with anyone. Is it because he is Nuer?”

Mohammed said witnesses who could not travel to Juba could testify via video or send a representative.

However, five survivors said they had not been called to testify, raising questions about the government’s ability to carry out a fair trial.

Two of the rape victims said they might return to Juba to testify if their anonymity and safety was guaranteed.

“The most important outcome for me is to end the culture of impunity,” said a Western woman sexually assaulted by four soldiers. “I don’t think it should just be about us and about our case, but about this larger issue of bringing justice to these crimes [committed against] many other people as well.”

Another Western aid worker, raped by 15 soldiers, said the accused are likely low-ranking and may have been recruited when they were children.

“I’m much more angry at the senior levels of the army who were aware of the attack, who knew and did nothing, or more senior soldiers who were there seeing these things happening and did little,” she said.

The then-commander of the presidential guard, Marial Chanuong, declined to comment. An army spokesmen did not answer calls.