An explosion of violence in the mineral-rich, northeastern district of Ituri since late last year has damaged efforts by the former Belgian colony to recover from a wider five-year war.
"The humanitarian situation has become catastrophic since the outbreak of fighting in December," said Modibo Traore, the head of the UN Office for the Coordination for Humanitarian Affairs (OCHA) in Ituri.
"We are now looking at about 100,000 displaced in all, including about 70,000 that are in the camps," he said on Monday.
Traore warned that UN military operations against militia in Ituri, which came just days after the killing of nine Bangladeshi peacekeepers this month, would make matters worse as armed men would vent their anger on long-suffering civilians.
He was speaking in Ituri's capital Bunia as Human Rights Watch (HRW) published a report saying government soldiers and rebels had raped tens of thousands of women in the east of Democratic Republic of Congo since fighting broke out in 1998.
Fighters on all sides of Congo's war have raped civilians on a massive scale, but only a few have ever been tried, HRW said.
"Sexual violence has shattered tens of thousands of lives in Congo, but fewer than a dozen victims have seen their assailants prosecuted"
Alison Des Forges,
senior adviser, HRW
"Sexual violence has shattered tens of thousands of lives in Congo, but fewer than a dozen victims have seen their assailants prosecuted," said Alison Des Forges, senior adviser to HRW's Africa division.
Fighting between ethnic-based militia in remote Ituri has killed more than 50,000 people since 1999. The latest clashes started in December between Hema and Lendu militia in the Djugu territory, not far from the border with Uganda.
The ethnic conflicts are rooted in commercial and land rivalries in a region rich in diamonds, gold and timber.
Civilians bear the full brunt of the brutality. Militias have razed villages, butchered several hundred people, kidnapped civilians and raped scores of women.