The court in Bunia, the capital of Ituri province in the north-east of the country, found nine defendants guilty of war crimes, rape, arson, pillaging and murder, UN spokesperson Marie Okabe told reporters in New York.
The court handed down lengthy sentences, including life in prison for the leader of the assault on 11 August 2006.
Most of the victims had been displaced by the violence in the vast Central African nation in recent years.
The UN mission, known as MONUC, said that although the ruling sends a strong message again impunity in the DRC, much remains to be done, including the prosecution of other similar cases.
In a related development, a UN independent expert said that violence against women in the DRC "seems to be perceived by large sectors of society to be normal."
Yakin Ertürk, the Special Rapporteur on violence against women, its causes and consequences, observed in a statement that "tragically, in a resource-rich country like DRC, poverty is all too striking and women disproportionately bear its hardships and burden."
Ms. Ertürk visited the country from 16 to 27 July, and focused primarily on sexual violence, which she said "is rampant and committed by non-state armed groups, the Armed Forces of the DRC, the National Congolese Police and increasingly also by civilians."
The situation in South Kivu province - which she said is the worst crisis she has come across so far - must be addressed immediately, she said.
The South Kivu Provincial Synergie on Sexual Violence, which brings together Government, UN and civil society representatives, has recorded 4,500 sexual violence cases in the first half of this year.
"The real number of cases is certainly many times higher as most victims live in inaccessible areas, are afraid to report or did not survive the violence," the Rapporteur said.
The atrocities - mostly committed by foreign non-state armed groups - are "of an unimaginable brutality that goes far beyond rape" and are "structured around rape and sexual slavery and aim at the complete physical and psychological destruction of women with implications for the entire society," she noted.
So far, the DRC armed forces, known as FARDC, have not been able to halt the violence against women in South Kivu. Therefore, Ms. Ertürk said, the international community and the Government must act urgently to bring an end to such atrocities.
The FARDC, the National Congolese Police (PNC) and other State security forces also commit acts of sexual violence which is not isolated to the country's troubled east. Particularly troubling is that major perpetrators of grave human rights violations are not excluded from being integrated into the regular armed forces, thus allowing a high number of such men to assume high ranks in the military.
The Rapporteur voiced alarm that in Equateur Province, the PNC and FARDC launch reprisal attacks targeting civilians and involving "indiscriminate pillaging, torture and mass rape." Last December, the 70 members of the PNC took revenge for the burning of a police station by torturing civilians and raping over three dozen women, as well as an 11-year-old girl, and yet no police officers have been charged or arrested, she said.