HRW says the pattern of sexual violence in Darfur has changed
Women and girls in Darfur are still subjected to widespread rape and sexual assault five years after the start of the conflict, Human Rights Watch says.
The New York-based group said neither the Sudanese security forces nor international peacekeepers were doing enough to protect women from attack.
Pro-government militias have been accused of using attacks on women to terrorise the civilian population.
Sudan's army has criticised a UN report accusing soldiers of raping women.
The report, released last month, said witnesses saw soldiers joining in attacks by the Janjaweed, raping girls and taking part in the looting of towns in West Darfur.
More than 200,000 people have died in Darfur since rebels took up arms in 2003, according to the UN. Two million have fled their homes.
Rape and sexual assault have been a constant feature of the humanitarian catastrophe in Darfur.
According to Human Rights Watch, as the conflict has become more complex, the pattern of sexual violence has changed.
The Janjaweed are accused of planning to terrorise civilians
Women and girls are now as likely to be assaulted in periods of calm as during attacks on their villages and towns.
Government soldiers, militiamen, and rebel fighters all also targeting women on the fringes of camps for displaced people spread around the region.
The Sudanese government has said it is committed to stopping the sexual violence, but in practice, little or nothing is being done.
Most victims are too afraid to report attacks. When they do, Sudanese police are usually unwilling or unable to act and soldiers are still effectively immune from civil prosecution.
The presence of UN and African Union peacekeepers has helped deter attacks in some areas.
But Human Rights Watch says they must extend their operations, providing patrols to protect women who venture outside the camps to gather firewood.
More women police officers and more sensitive procedures to help victims are also required, it says.