Government-backed Arab militia are raping, abducting and disabling girls as young as eight in the Sudanese region of Darfur, Amnesty International claims.
The organization said hundreds of interviews with refugees who have fled to neighbouring Chad have revealed an horrific pattern of systematic abuse by Janjaweed bands, often helped or watched by the Sudanese army.
It called for a UN resolution to condemn rights abuses in Darfur, where rebels began a revolt last year amid conflict between black African villagers and Arab nomads.
"Girls as young as eight are among the victims of mass rape in Darfur," Amnesty said in its report.
"In some cases women are having their arms or legs broken in rape attacks and mass abductions are also taking place, with women as old as 80 taken hostage and used as sex slaves."
Amnesty said it had collected the names of 250 raped women and had information of at least another 250 cases. "In almost all the attacks, the government's army were either directly involved or direct witnesses," it said.
Rapes often took place in public, involved extreme violence, and included pregnant women, the group added.
"Whole families and entire villages are traumatised by these almost unimaginable acts of violence and sexual torture," Amnesty International UK Campaign Director Stephen Bowen said.
"The Sudanese government's army is clearly complicit . . . and the international community must confront the Sudanese authorities with this fact."