Two weeks after Khartoum’s tanks, artillery, and military aircraft began moving into South Kordofan, violence—especially against civilians—continues to explode. There are now scores of reliable reports that attacks against the indigenous Nuba people have accelerated, both on the ground and from the air. Humanitarian conditions are deteriorating rapidly, aid workers are fleeing the region, essential relief supplies have been looted in the regional capital of Kadugli, and the U.N. World Food Programme has indicated that the violence could prevent it from reaching the 400,000 people it was serving before the recent onslaught. There are no verified estimates of the number of people displaced, but Abdel Aziz El Hilu, former governor of South Kordofan, has put the number at almost half a million. Dozens have been reported killed, but, in the absence of any effective humanitarian monitoring, this surely understates significantly.

For its part, Khartoum has ominously promised to continue fighting. Troops and military vehicles are still pouring into Kadugli; according to U.N. observers, some 280 military vehicles have been spotted, and “preparations for a major ground offensive” are being made. Understandably, according to a report by the U.N. Office for the Coordination of Humanitarian Affairs, this has created “a growing sense of panic” among the Nuba.

These highly provocative military actions—on top of those occurring in Abyei and parts of southern Sudan—put all of Sudan at risk of renewed civil war. Complicating matters is a weak U.N. peacekeeping mission in South Kordofan that, even before it became subjected to this most recent violence and harassment, was barely able to protect itself, let alone the civilians seeking its refuge. Indeed, it has a poor reputation among the Nuba people. (Several Egyptian members of the U.N. mission have even been accused of assisting in ethnic roundups.)

And, ultimately, the Nuba are at the crux of this conflict. It’s the Nuba people, of multiple African ethnicities, and their way of life that seem to be the primary targets of the recent violence. They are being attacked not only by Khartoum’s regular military forces but by the notorious Arab militias known as the Popular Defense Forces (PDF). And this fact, inevitably, raises questions about whether what we are witnessing is ethnic cleansing—or, worse, genocide.

There is an extraordinary amount of information being smuggled out of South Kordofan by fleeing aid workers and civilians and conveyed via electronic communication, including digital photographs. And, from the mounting evidence that has come to me, clear patterns emerge. The signature feature of Khartoum’s operation is the door-to-door roundup of Nuba, who are often summarily shot. The Nuba are also stopped at checkpoints grimly similar to those once seen in Rwanda. One aid worker who recently escaped from South Kordofan, told McClatchy, “Those [Nuba] coming in are saying, ‘Whenever they see you are a black person, they kill you.’” Another Nuba aid worker reports that an Arab militia leader made clear that their orders were simple: to “just clear”