A local parliamentarian blamed army soldiers for the violence.
“Our teams have treated since Tuesday more than 100 people who were victims of rape or physical violence between June 10 and 12,” said Megan Hunter, head of the Dutch branch of MSF in Sud-Kivu province.
The attack was in the Sud-Kivu village of Nyakiele, she said.
Provincial parliamentarian Jean-Marie Ngoma said “soldiers from the Congolese army” headed by a colonel who was a former member of the Mai Mai militia were responsible.
More than 60 women in the village were raped, he said.
The resource-rich eastern DR Congo is an unstable area marked by violence blamed largely on the presence of several militia groups and soldiers.
The vast central African country has a high incidence of rape, with a study released in May saying more than 1 100 women were raped every day.
More than 400 000 women and girls between the ages of 15 to 49 were raped in the conflict-ravaged country during a 12-month period in 2006 and 2007, according to the study published in the American Journal of Public Health.