Sudan's paramilitary Rapid Support Forces (RSF) and allied militias are committing widespread sexual violence in southern Sudan, the New York-based Human Rights Watch (HRW) said Monday.

It is the latest such report by international monitors alleging sexual violence during Sudan's 20-month war which has led to what the United States called the world's worst humanitarian crisis.

In its new report, HRW said it had documented dozens of cases since September 2023 involving women and girls aged between 7 and 50 who were subjected to sexual violence, including gang rape and sexual slavery, in South Kordofan state.

The latest details follow a separate report last week from the watchdog which more broadly accused the RSF and allied militias of carrying out numerous abuses, mainly against ethnic Nuba civilians, in South Kordofan state from December 2023 to March 2024.

These attacks, it said, "had not been widely reported" and constituted "war crimes."

Parts of South Kordofan and parts of Blue Nile state are controlled by the Sudan People's Liberation Movement-North (SPLM-N), a rebel group.

The SPLM-N faction led by Abdelaziz al-Hilu refused to join other Sudan rebels in signing a 2020 peace deal with the government, as Hilu sought a secular state as a prerequisite.

Many South Kordofan residents are members of Sudan's Christian minority.

Hilu also at that time refused talks with RSF leader Mohamed Hamdan Daglo, linking him with atrocities.

SPLM-N has clashed with both the army and RSF in parts of South Kordofan since April 2023, when the war between the paramilitaries and Sudanese Armed Forces began, HRW said.

The conflict has claimed the lives of tens of thousands of people, internally displaced more than 8 million, according to the U.N. and forced more than 3 million others to seek safety in neighboring countries.

'They kept raping me'

According to the HRW report, many of the victims were gang-raped at their or their neighbours' homes, often in front of families while some were abducted and held in conditions of enslavement.

One survivor, a 35-year-old Nuba woman, described being gang-raped by six RSF fighters who stormed her family compound and killed her husband and son when they tried to intervene.

"They kept raping me, all six of them," she said.

Another survivor, aged 18, recounted being taken in February with 17 others to a base where they joined 33 detained women and girls.

"On a daily basis for three months, the fighters raped and beat the women and girls, including the 18-year-old survivor, crimes that also constitute sexual slavery," HRW said.

At times, the captives were even chained together, it said.

"These acts of sexual violence, which constitute war crimes ... underscore the urgent need for meaningful international action to protect civilians and deliver justice," HRW said in its report.

The U.N.'s humanitarian chief Tom Fletcher raised the alarm late in November over an "epidemic of sexual violence" against women in Sudan, saying that the world "must do better."

In October, the United Nations Independent International Fact-Finding Mission for the Sudan said both sides have committed abuses including torture and sexual violence. But it accused the paramilitaries, in particular, of "sexual violence on a large scale."

These included "gang rapes and abducting and detaining victims in conditions that amount to sexual slavery," the mission said.

In its initial report last week, HRW urged the U.N. and African Union to "urgently deploy a mission to protect civilians in Sudan."