YIDA, South Sudan

A GREAT humanitarian catastrophe and vicious ethnic cleansing is unfolding here in the remote and impoverished region where Sudan and South Sudan come together.

For some in the Nuba Mountains, living in thatch huts far from electricity or paved roads, the sharpest acquaintance they are making with 21st-century technology is to be bombed by Sudanese aircraft.

Bombings, ground attacks and sexual violence — part of Sudan’s scorched-earth counterinsurgency strategy — have driven hundreds of thousands of people from their homes in South Kordofan, the Sudanese state where the Nuba Mountains are located. In some ways, the brutality here feels like an echo of what Sudan did in Darfur, only now it is Nubans who are targets.

“They said that they want to finish off the black people; they said they want to kill them all,” recalled Elizabeth Kafi, a 22-year-old Nuban who said she was kidnapped in December by Sudanese uniformed soldiers. She and others say that the mostly Arab Sudanese soldiers scorn Nubans partly for their darker skin, partly because some are Christian, but mostly because many Nubans back an armed uprising against decades of Sudanese misrule. In 23 days of captivity, she said she saw the soldiers use guns to execute several Nuban men, including her grandfather and brother-in-law. She described watching soldiers gang rape and then cut the throat of a young Nuban woman, and also stab to death the woman’s 3-year-old son.