A United Nations report has accused Sudanese authorities of taking no action against militiamen and soldiers accused of rape in the Darfur region.
Darfur women and girls are afraid of leaving their camps
Women in refugee camps risk being raped if they go in search of food, the UN's human rights commissioner says.
International charity Medecins Sans Frontieres said in June that 500 women had been raped in four months alone.
Sudan's authorities have threatened and arrested victims to make them withdraw the charges, the UN report says.
More than two million people have been forced from their homes and at least 180,000 have died during the Darfur conflict.
Sudanese authorities deny accusations that they back the Arab Janjaweed militias who are alleged to have committed widespread atrocities, such as mass killings and mass rape.
"Every week, more new cases of rape of women and girls are reported," the UN report said.
"The government of Sudan needs to acknowledge the scope of the problem and to take concrete action to end the climate of impunity in Darfur," it said.
The UN says charges are still not investigated thoroughly by the authorities.
Human Rights Commissioner Louise Arbour told the UN Security Council ahead of the report's release on Thursday that Khartoum's government appeared "either unable or unwilling to hold them consistently accountable".
Ms Arbour said that rape victims themselves could face criminal charges when courts ruled that they were unable to prove their cases - discouraging women from making accusations.
"Arrest, harassment and intimidation of victims of sexual violence and their supporters must end," the UN report said.
In June, Sudan set up a special court to try those accused of war crimes in the Darfur region but the report said it was too early to judge its impact.
"To date, most perpetrators have not been brought to justice, and it remains to be seen whether [the court] will effectively address the crime," the report said.
It urged the Sudanese government to remove all regulations granting immunity to state officials from prosecution and to give thorough training to police, prosecutors and judicial authorities in the investigation of sexual crimes.