Congolese troops fleeing the M23 rebels last November raped at least 97 women and 33 girls, some as young as 6, according to a UN report.
The report, released on Wednesday covered "mass rape, killings, and arbitrary executions and violations resulting from widespread looting," UN spokesman Martin Nesirky told reporters.
A report by the UN Joint Human Rights Office said most of the rapes took place over November 22-23 in the eastern Congo town of Minova.
The report states: "One or two of the soldiers would leave with the looted goods and at least one would stand guard as the remaining (Congolese) soldiers raped women and girls in the house. Victims were threatened with
death if they shouted; some were raped at gunpoint. Most victims were raped by more than one soldier."
"The victims included 33 girls aged between 6 and 17," Nesirky said.
During the rebel occupation of the towns of Goma and Sake, the M23 "perpetrated serious violations of human law and gross human rights violations," Nesirky said, including at least 59 cases of sexual violence.
The mass rapes occurred in November, 2012, after the Congolese army was defeated by the M23 rebels who seized the provincial capital of Goma, in the Democratic Republic of Congo's troubled east. The national army retreated in disorder.
Commanders lost control of their troops, or were unwilling to impose discipline over their men who regrouped some 50 kilometers south of Goma, in Minova.
A small, dusty town on the shore of lake Kivu, Minova is home to several thousand people. For days, the Congolese army raped, killed and looted in anger after their defeat, before discipline could be re-established by army commanders.
The report says 11 Congolese soldiers have been arrested by the Congolese military prosecutor's office, "including two for murder, but only two for related cases of rape." The other charges were not specified.
The commanding officers and deputy commanding officers of the two main battalions suspected of committing these acts, as well as officers of eight other units, have been suspended, the UN said.
Military magistrates from both North Kivu and South Kivu, UN peacekeeping and humanitarian agency staff travelled to Minova and surrounding villages from Feb. 6-13, and "military investigators took testimony from several hundred victims, including a large number of victims of sexual violence," the report said.
Roger Meece, head of the UN mission in Congo, said the investigation "should be pursed in an independent and credible manner."
"Those responsible for such crimes must know that they will be prosecuted," UN High Commissioner for Human Rights Navi Pillay said in a statement, calling the sexual violence outlined in the report "horrifying" in scale and systematic nature.