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 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 (MSF) last week said 125 women and girls had been raped while walking to emergency food distribution centers set up by international aid agencies.At war since 2013, South Sudan has seen horrific levels of sexual violence. * Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. In the first half of 2018, some 2 300 cases were reported, the vast majority of those targeting women and girls. More than 20% 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 underreported.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.