Armed men, many in uniform, carried out the attacks near the northern city of Bentiu, according to the UN aid agencies.

More than 150 women and girls have come forward in the past 12 days to seek help in South Sudan after they were raped or suffered other forms of sexual violence, the heads of three UN agencies said on Monday.

Armed men, many in uniform, carried out the attacks near the northern city of Bentiu, according to a joint statement from Henrietta Fore, who heads the UN children’s agency UNICEF, UN aid chief Mark Lowcock and the director of the UN Population Fund, Natalia Kanem.

The three agencies condemned “these abhorrent attacks” and called on South Sudan authorities to ensure the perpetrators face justice.

Doctors Without Borders, known by its French initials MSF, last week said 125 women and girls had been raped while walking to emergency food distribution centres set up by international aid agencies.

UN Secretary-General Antonio Guterres condemned the attacks.

“These horrific acts are a distressing reminder of how, despite recent recommitments by South Sudan’s leaders to a cessation of hostilities and a revitalised peace agreement, the security situation for civilians remains dire, especially for women and children,” he said in a statement.

He urged all parties to the conflict and future leaders in South Sudan “to ensure the safety of civilians and address impunity for these crimes through investigation and prosecution of perpetrators.”

At war since 2013, South Sudan has seen horrific levels of sexual violence.

In the first half of 2018, some 2,300 cases were reported, the vast majority of those targeting women and girls. More than 20 percent of the victims were children, the UN statement said.

The three agencies said the actual number of rapes was far higher because the violence is severely under-reported.

As well as being raped, MSF said many of the victims were “whipped, beaten or clubbed with sticks and rifle butts” and robbed of their clothes, shoes, money and the ration cards entitling them to food aid.

“In more than three years of working in South Sudan, I have never seen such a dramatic increase in survivors of sexual violence arriving at our programmes looking for medical care,” said Ruth Okello, a MSF midwife in South Sudan.

A UN panel of experts last month said in a report to the Security Council that there were “alarming levels” of sexual violence and human rights abuses in South Sudan.

The council is due to discuss the crisis in South Sudan on December 18.