(CNN) -- More than two dozen children were among the hundreds raped by armed rebels in the war-torn eastern Democratic Republic of Congo, the United Nations said.
Twenty-seven minors, including one boy, were among the victims, the U.N. said Friday. One attempted rape was also reported.
The children were among 240 people raped by Rwandan and Congolese rebels who raided villages in North Kivu province between July 30 and August 3, aid groups said. Attackers blocked roads and prevented villagers from reaching outside communications. Many homes were also looted.
Many of the victims were raped by two to six men, according to the United Nations Organization Stabilization Mission in the Democratic Republic of the Congo (MONUSCO).
MONUSCO, the United Nations peacekeeping force in the country, raised the number of victims after earlier reports put it at 156.
Since the rapes were first publicly reported on August 22, more victims have come forward, the force said.
The United Nations has said it did not learn about the attacks until August 12, when it was alerted by International Medical Corps.
International Medical Corps said it first told the United Nations about the rapes on August 6.
A July 30 internal U.N. e-mail that was relayed to relief agencies working in the area warned that the rebels had taken over the villages, and had already committed one instance of rape.
The town of Mpofi, 52 kilometers from Walikale, had just fallen into the hands of the Democratic Forces for the Liberation of Rwanda, a rebel group.
"A woman was raped there," the e-mail said in French. "Humanitarian workers are said not to go there."
On August 10, the United Nations posted an online bulletin saying that 25 women had been raped in the villages, contradicting statements made by U.N. military spokesman Madnoje Mounoubai and special representative Roger Meece.
Asked to explain the discrepancy, deputy U.N. spokesman Farhan Haq told reporters this week: "We are aware of the existence of a number of e-mails and we are trying to trace exactly how those e-mails were responded to."
He said that about 80 peacekeepers were conducting patrols in an area about four times the size of Manhattan.
"The question is -- how much area could they cover, and were they able to get into the areas where they needed to be, where the relevant information was?"
U.N. officials have said they will toughen efforts to stop rapes in the region.
"The recent mass rapes underscores the need for an end to impunity for perpetrators of such crimes," said Margot Wallstrom, a U.N. special representative for sexual violence in conflict.
These attacks reinforce that "you cannot have a policy of zero tolerance backed by zero consequences," she said.