A researcher at Yale University in the United States says the paramilitary Rapid Support Forces (RSF) are digging mass graves in el-Fasher, the city in Sudan's western Darfur region that has seen mass killings and displacement since the RSF took over last month. Nathaniel Raymond, executive director of the Humanitarian Research Lab at Yale's School of Public Health, told Al Jazeera on Tuesday that the RSF have begun to dig mass graves and to collect bodies throughout the city.