An international human rights group has accused pro-government militias in the Darfur region of Sudan of using rape and other forms of sexual violence "as a weapon of war" to humiliate black African women and girls as well as the rebels fighting the government in Khartoum.

In a report to be released Monday, Amnesty International said the sexual attacks in Darfur amounted to war crimes and crimes against humanity. But it said it did not have sufficient evidence to show that the Janjaweed, as the government-backed militias are known, have carried out genocide in Darfur, as some critics of Sudan's government maintain.

"The horrific nature and scale of the violence inflicted on entire groups in Darfur appears to be a form of collective punishment of a population whose members have taken up arms against the central government," the Amnesty International report said.

"It may be interpreted as a warning to other groups and regions of what could happen to the local population if certain groups decided to rebel against Khartoum," it added.

Amnesty International called for the creation of a commission of inquiry to investigate and bring to justice those responsible for sexual violence against the women of Darfur.

Rape is a cultural taboo in Sudan and families often ostracize victims. Although rape has been so widespread over the last year that many women feel emboldened to discuss it, many others are believed by experts to be denying that it ever occurred.

"The suffering and abuse endured by these women goes far beyond the actual rape," Amnesty said. "Rape has a devastating and ongoing impact on the health of women and girls, and survivors now face a lifetime of stigma and marginalization from their own families and communities."

Sudan ordered Saturday that committees of women judges, police officers and legal consultants investigate rape accusations and help victims through criminal cases, The Associated Press reported.

In many interviews, women recounted vicious rapes by members of the Arab militias. One woman from Silaya, near the town of Kulbus in western Sudan, was five months pregnant when she was abducted with eight other women in July 2003.

"Five to six men would rape us in rounds, one after the other for hours during six days, every night," the woman, who was identified only as S., told Amnesty researchers. "My husband could not forgive me after this; he disowned me."

Amnesty International said it had received many reports of militia men pulling out the fingernails of women to force them to reveal the locations of their husbands. During such interrogations, the women were accused of being rebel sympathizers.

Women have also been subjected to racial insults because their skin is darker than that of the Arabs.

"You blacks, you have spoiled the country," one in a group of women recounted the militia men telling them. "We are here to burn you. We will kill your husbands and sons, and we will sleep with you! You will be our wives!"

www.nytimes.com/2004/07/19/international/africa/19suda.html