The only foreigner to come forward and give evidence in a high-profile South Sudan trial where army troops are accused of gang rape and murder in a hotel rampage a year ago is urging other survivors to speak up.

The trial is a key test of accountability in a civil war-torn country where few accused of atrocities ever face justice. Twelve South Sudanese soldiers are accused of gang-raping five foreigners, killing a local journalist while forcing survivors to watch, and looting the Terrain Hotel compound in the capital, Juba.

"Men have an equal or greater responsibility to come forward," the Italian woman told The Associated Press after testifying last week. "Men don't face the same risk of sexual violence and they can stand up against these crimes." She spoke on condition of anonymity for fear of retribution.

READ MORE: South Sudan soldiers face trial for rape and murder

The attack occurred shortly after fighting erupted in the capital in July 2016 between President Salva Kiir's forces and troops loyal to former Vice President Riek Machar.

An AP investigation last year exposed graphic details of the Terrain assault, including victims' pleas for help to a nearby UN base that brought no immediate response. A UN investigation led to the firing of the commander of the peacekeeping force there. The United States government has pressed South Sudan to hold the soldiers accountable and offered support for the investigation.

The trial almost collapsed last month when judges with the military court threatened to dismiss the charges of rape and murder unless the foreign victims and witnesses testified. The judges initially rejected the possibility of remote testimony via online video interviews, which they've now accepted.

The Italian woman, who had been working in the humanitarian sector in South Sudan, said she was afraid to return to the unstable East African nation because she was frightened the assault could happen again.

She said she decided to return and testify in order to give a "voice to the millions of victims in South Sudan who don't have a voice".

She said she identified four of the accused in the courtroom, saying when she looked at them one by one she "immediately recognised them".

Her testimony "gave credibility to the trial" and filled a gap when it came to the rape charges, said a lawyer representing the assault victims, Philips Anyang Ngong.

Human rights workers monitoring the trial have praised the woman's decision to return to South Sudan to give her testimony.

"We applaud the victim for appearing at trial. We hope this proceeding is a first step towards addressing the much larger problem of impunity for serious human rights crimes in South Sudan," said Joanne Mariner, senior crisis adviser at Amnesty International.

READ MORE: South Sudan: UN reports campaign of killing and rape

Jehanne Henry, senior Africa researcher for Human Rights Watch, said: "This case is a test of South Sudan's willingness to prosecute soldiers for crimes against civilians, especially sexual violence."

During South Sudan's four years of civil war, rape has been used as a weapon with impunity, according to rights groups. The country is suffering from sexual violence on a "massive scale", a recent report by Amnesty said.

The trial is expected to continue in late October. It is unclear whether anyone else will give evidence, in person or remotely.