A U.N. investigation revealed Wednesday that Sudan's Rapid Support Forces carried out mass killings, abducted women and girls, committed gang rapes and used starvation as a weapon during last year's siege and capture of a city, in what it said was a deliberate campaign amounting to genocide.

The Rapid Support Forces, which are battling the Sudanese army in a civil war, committed the crimes in el-Fasher in north Darfur, which they captured last year after a long siege, the U.N. Fact-Finding Mission for Sudan found.

Survivors described being raped in rooms where bodies of recently killed civilians, including their own family members, were still lying on the ground.

The report found that the RSF and allies committed the war crime of starvation by imposing a prolonged siege on the city, impeding relief supplies, ⁠and ⁠shelling food production systems.

The RSF has denied such abuses in over three years of civil war, saying the accounts have been manufactured by its enemies and making counteraccusations against them.

The U.N. human rights chief warned on Friday that a similar "catastrophe" was unfolding around another large city, al-Obeid, the capital of North Kordofan state, and that his office had documented patterns of summary executions, abductions, torture and sexual violence in the surrounding region.

Members of ⁠the U.N. human rights council on Monday condemned the violence and set up an urgent inquiry into alleged abuses there.

Britain and other states have warned of a risk of large-scale atrocities ​as the RSF massed forces around al-Obeid, now home to around half a ​million people, including more than 83,000 internally displaced people.

The fact-finding mission had already concluded in a previous report in February that mass killings ⁠of non-Arab ‌communities when ‌the RSF captured el-Fasher bore hallmarks of genocide.

Its new ⁠report said it found additional evidence that ‌the widespread and systematic pattern of conduct of the RSF, including large-scale killings, mass rape and ​deliberate starvation, was part of an ⁠intended policy.

"The patterns we documented in el-Fasher – including encirclement, ⁠attacks on civilian infrastructure, restrictions on humanitarian access, and widespread abuses against civilians – ⁠serve as a ​stark warning," said Mohamed Chande Othman, the mission's chair.

"The international community must heed these lessons and act to prevent further catastrophe," he added.