Bukavu, Democratic Republic Of Congo (CNN) -- Many of Congo's rape survivors took to the streets Sunday to speak out against sexual violence in a country where it has become a weapon of war.

"My heart is in pain, why are you raping me?" sang the rape victims, many of whom left hospital beds to join the march in eastern Congo.

"They have had enough, enough, enough, enough," said Nita Vielle, a Congolese women's activist, of the women marching. "Enough of the war, of the rape, of nobody paying attention to what's happening to them."

The United Nations has named the Democratic Republic of Congo the "rape capital of the world," with 15,000 women raped in eastern Congo last year. The attacks occurred in parts of the country where armed rebel groups moved into areas considered to be pro-government but lacking in army or police protection, according to the U.N.

Margot Wallstrom, the U.N. secretary-general's special representative on sexual violence in conflict, said recently that one distraught Congolese woman had told her that "a dead rat is worth more than the body of a woman."

"It was an expression of how human rights violations against women are still the lowest on a fool's hierarchy of war time horrors," she said.

Sunday's march was organized by the World March of Women in association with local women's groups. Organizers hoped the march would combat the stigma attached to rape victims and draw international attention to the problem of rape as a war tactic.

"It's just great to have so many women out on the streets," said Celia Alldridge, a representative from World March of Women. "We believe that women should not be made prisoners in their own homes."

Among throngs of marchers, many clad in bright traditional garb and carrying homemade signs, one Congolese marcher echoed that sentiment.

"I tell you, it's a wonderful thing to see all the women together, just for one reason -- for the peace of the women of Congo," said Mary Georges. "This is the freedom of the Congo women."

Last month, a U.N. report slammed Congo's security forces for failing to prevent a wave of mass rapes over several days during the summer.

The preliminary report confirms the rape of at least 303 civilians between July 30 and August 2 in the Walikale region of Congo's North Kivu province.

The report points to serious shortcomings in the preparedness and response of the local detachments of the Congolese army and the police stationed in the area.

It also notes that their failure to prevent or stop the attacks was compounded by subsequent failings on the part of U.N. stabilization mission forces in Congo.

The report said the force had not received any specific training in the protection of civilians, and suffered from a number of operational constraints, including a limited capacity to gather information, as well as the lack of a telecommunications system in the area.

"The scale and viciousness of these mass rapes defy belief," said U.N. High Commissioner for Human Rights Navi Pillay.

"Even in the eastern part of DRC where rape has been a perennial and massive problem for the past 15 years, this incident stands out," Pillay said, "because of the extraordinarily cold-blooded and systematic way in which it appears to have been planned and executed."