Medecins Sans Frontieres said the violence by members of a shadowy Ugandan rebel group called the Lord's Resistance Army started in a remote region of northern Congo last year and has recently spread to nearby areas. Few other humanitarian agencies are working in the area, which has few roads.
The aid group, also known as Doctors Without Borders, presented a video of victims' testimony at a news conference in South Africa. One man said he had been abducted with his brother, who tried to escape. He was forced to recapture his brother and club him to death.
"If I hadn't done it, they would've have killed me too," he said.
His name and the names of others who appeared in the video were withheld by MSF to protect them from possible reprisals for speaking out. In the video, a 15-year-old girl and an 18-year-old woman described being captured and raped.
"They told me they were going to make me someone's wife, but I refused, and they hit me with a knife," the woman said. "I was wounded in the leg. So I had to accept."
Meinie Nicolai, MSF's operational director, said in South Africa Wednesday her group could not address the political question of how to stop the violence. But she said: "There needs to be respect for the civilian population."
She said the work was dangerous.
"The security situation for humanitarian workers is not easy," she said. But "we're not saying it's impossible. And the needs in the area are increasing."
The mysterious LRA is notorious for mutilating victims and abducting children _ forcing the boys to fight and the girls to become rebels' concubines. It has been waging an insurgency in northern Uganda for more than 20 years, and the conflict spilled over into Congo about five years ago.
Congo, which is the size of Western Europe but has poor infrastructure and little government oversight, is fraught with violent groups.
Earlier this week, humanitarian groups said that fighters in eastern Congo have killed more than 1,000 civilians and displaced some 900,000 since January. The report released by a coalition of 84 organizations said that many of the killings were carried out by Rwandan Hutu militiamen. Congolese government soldiers also have targeted civilians, the report said.