GOMA, Democratic Republic of Congo  A mob of Rwandan rebels gang-raped at least 150 women last month during a weekend raid on a community of villages in eastern Congo, United Nations and other humanitarian officials said Sunday.

The United Nations blamed the Democratic Forces for the Liberation of Rwanda, or F.D.L.R., for the attack. The F.D.L.R. is an ethnic Hutu rebel group that has been terrorizing the hills of eastern Congo for years, preying on villages in a quest for the natural resources beneath them.

The raided villages are near the mining center of Walikale, known to be a rebel stronghold, and are “very insecure,” said Stefania Trassari, a spokeswoman for the United Nations Office for the Coordination of Humanitarian Affairs. “Rape is something we get quite often.”

But she and other United Nations and humanitarian officials said that this attack was unusual because of the large number of victims and the fact that they were raped by more than one attacker simultaneously.