Congo Friday arrested a senior army commander accused of ordering the rapes in Fizi on New Year's Day. The arrest followed the detention of 10 other soldiers earlier in the week.
Human rights officers from the UN peacekeeping mission had originally said more than a dozen women were raped. But investigators have since documented at least 67 victims in South and North Kivu provinces, including a teen-ager and two pregnant women.
Navi Pillay, the UN High Commissioner for Human Rights, called on Congolese authorities to investigate "these hideous crimes" and prosecute alleged perpetrators as soon as possible.
"The High Commissioner remains extremely concerned with the fact that the Congolese army remains responsible for a significant number of human rights violations, including sexual violence, against their own population," a UN statement said.
Rights groups and the UN peacekeeping force are putting pressure on the central African state to crack down on rogue elements in its military.
Pillay said that the soldiers arrested last week, including Lt. Colonel Kibibi Mutwara and three majors, were expected to go on trial "shortly." Kibibi has denied the charges.
Sexual violence is a regular occurrence in eastern Congo, which continues to suffer from conflict after a brutal civil war that ended in 2003 in which more than five million people died.
Last year hundreds of people were raped by members of the FDLR, a Rwandan Hutu militia operating in eastern Congo, and the army has also regularly been accused of carrying out atrocities.
