-- On the morning of July 12, hell descended on the village of Donki Dereisa. Shortly before sunrise, Fatima Ibrahim, 28, awoke to the deafening sound of exploding ordnance falling from the sky. As she emerged from her mud hut with her 10-year-old daughter, she saw fires blazing all around and scores of heavily armed men on horseback attacking from every direction. With bullets whistling past, Ibrahim and her daughter ran for their lives, ducking into a nearby ravine, where they hid without food or water for the next two days.

From the ditch, Ibrahim witnessed a horrific avalanche of violence that will haunt her for life. With Sudanese foot soldiers at their side, the mounted attackers shot the panicked and unarmed villagers in cold blood. Approximately 150 people, including 10 women, were killed. But the worst was to come.

Ibrahim told Refugees International about a week after the attack that among those captured during the assault were four of her brothers and six young children, including three of her cousins. As Ibrahim watched in horror, several of the attackers began grabbing the screaming children and throwing them one by one into a raging fire. One of the male villagers ran from his hiding place to plead for their lives. It was a fatal error. The raiders subdued the man and later beheaded him and dismembered his body. All six of the children were burned. Ibrahim's four brothers have not been heard from since.

The violence in Donki Dereisa is part of a broader conflict that began between government and rebel forces in March 2003. Since then the Sudanese government has exploited the rising tension between the impoverished African villagers who form the rebels' base and the nomadic Arab herders who have been competing with them for what remains of the region's arable land after decades of deforestation.

Armed to the teeth by the Sudanese government, hordes of mounted nomadic warriors, known locally as the Janjaweed, have waged a war of terror against Darfur's African population that has claimed the lives of as many as 50,000 defenseless civilians and driven more than 1.2 million from their homes. While many have fled to Chad, most of the displaced languish in squalid camps dispersed throughout Darfur, where they lack food, clean water and other necessities. International relief workers warn of famine, epidemics and a death toll that could reach into the hundreds of thousands.

In an effort to stop the killing and head off a looming humanitarian disaster, Secretary of State Colin Powell and U.N. Secretary General Kofi Annan visited Sudan this summer. On July 3, the United Nations and the Sudanese government issued a joint communique in which Khartoum formalized commitments it had made to Powell and Annan to immediately disarm the Janjaweed, prosecute egregious abuses of human rights and honor a cease-fire agreement reached two months earlier.

But recent events suggest that in making these commitments, Khartoum's objective was to stall for time in the hope it might deceive the international community into believing the crisis had been brought under control. This cynical approach is graphically illustrated by the recent arrest and prosecution of a group of alleged Janjaweed militiamen on charges of robbery and murder in southern Darfur's provincial capital of Nyala. According to reliable sources inside the government, the "Janjaweed" were in fact common criminals plucked from a Nyala jail, who were informed that they would be sentenced to death unless they agreed to pose as Janjaweed and confess to the crimes. The true killers remain at large.

Nor is there any indication that Khartoum intends to disarm or otherwise rein in the Janjaweed. To the contrary, the government and the Janjaweed have continued jointly and relentlessly to pursue their terrorist campaign in the few remaining regions of Darfur under government control where African villagers have not yet been driven from their homes.

Ironically, at the same time that it has been sponsoring these assaults, the Sudanese government has been aggressively attempting to persuade the displaced people of Darfur to return home. But returnees have been killed, beaten, raped and threatened by roaming bands of Janjaweed. It is hardly surprising that most of the displaced have heeded the Janjaweed's warning and spurned the government's invitation to return home. The government, however, appears to be committed to its policy of repatriation, and there is a danger that in the face of continued resistance by the displaced it will begin to forcibly return people en masse and declare an end to the crisis. If that happens, they will all be vulnerable to the same kinds of deadly violence that caused them to flee in the first place.

World leaders cannot afford to sit idly by while Khartoum continues to play games with the lives of its people. Consistent with its international commitments, the government of Sudan must immediately end offensive operations against its civilian population, disarm the Janjaweed and permit deployment of U.N. human rights monitors throughout Darfur. Yesterday the U.N. Security Council adopted a resolution calling on Sudan to disarm the Janjaweed and accelerate the flow of humanitarian aid. Now the United Nations must make sure that Khartoum complies.

The writer is a Washington lawyer and president of the George Wolf Operating Foundation. He has just returned from a fact-finding mission in Sudan with Refugees International.