GENEVA/JUBA (Reuters) - Rape and sexual violence against women and girls as young as eight is still widespread in northern South Sudan despite the signing of a peace deal to end the civil war in September 2018, according to a U.N. investigation published on Friday.

The report by the United Nations human rights office and the U.N. mission in South Sudan recorded 175 cases, mainly rapes lasting hours by multiple uniformed and armed men, just between September and December 2018.

Rape and gang rape in northern Unity state has reportedly continued this year, with perpetrators apparently thinking they could get away unpunished, U.N. High Commissioner for Human Rights Michelle Bachelet said in a statement.

The aid agency Médecins Sans Frontières said last November it had treated 125 women and girls who were allegedly raped or gang raped over a 10-day period.

The United Nations said most perpetrators were reportedly members of youth militia groups and elements of forces loyal to First Vice President Taban Deng Gai and the South Sudan People’s Defence Forces -- the national army -- into which Taban Deng Gai’s forces are being integrated.

A senior government official in the capital Juba told Reuters the report was not realistic and he accused NGOs of using the issue to raise money.

“Nobody can imagine that more than one hundred women are raped in just a one month without information leaked to the parents, to their husbands or to their brothers,” said Dhieu Mathok Diing, a minister in President Salva Kiir’s government.

“When you talk about the sexual violence, you can get money. This is unethical...they are people who are using this as a business which is really very bad.”

The report said South Sudan’s police and military had acknowledged the situation and planned to step up patrols and, although an inquiry led by the minister for gender had concluded the allegations were “unfounded and baseless”, Kiir had set up a committee with greater powers to investigate.

Mathok said the committee would soon release its findings.

“If found that it is true, those who did this will face justice and also if found not true, those who went out and released the report without justification will also face justice,” Mathok said.

The United Nations called for an independent investigation and said the government and leaders of armed groups must hold to account any perpetrators within their ranks.

It also called on the government to keep its promise to create a court consisting of South Sudanese and other African judges to try people accused of atrocities.

The U.N. peacekeeping mission had stepped up patrols and cleared foliage from roads to make it more difficult for men to ambush women, and was also working with local authorities to set up a mobile court to hear cases involving serious crimes, including sexual violence, the report said.