A Congolese colonel accused of leading his troops on a multi-day rampage and mass rape has turned himself.

A military spokesman for the Democratic Republic of Congo said Friday that the colonel, known as Kifaru, surrendered Thursday with about 100 of his men.

Some DRC officials accused Colonel Kifaru and his men of pillaging Nakiele, in South Kivu province, this past June after deserting the army. United Nations investigators say they have confirmed at least 121 cases of rape during the three-day incident.

The United States has said it is “gravely disturbed” by the attacks. State Department spokeswoman Victoria Nuland said the U.S. is working to provide support to the survivors and to help track down, arrest and prosecute those responsible.

United Nations officials have previously called Congo “the rape capital of the world.” They say an atmosphere of impunity allows soldiers, rebel fighters, and civilians to rape women and children without fear of arrest.

Earlier this week, the U.N. said an investigation into mass rapes last year in the Democratic Republic of Congo had been called off after some of the victims were attacked.

At least 387 women, men, and children were raped in several villages in eastern Congo's North Kivu province in late July and early August of last year.

The U.N. accuses former Congolese government troops, Congolese Mai-Mai militia and Rwandan Hutu rebels of carrying out the attacks. So far, only one person has been charged with any crimes.

The U.N. peacekeeping force in Congo has been criticized for not preventing the rapes in July and August.

There are currently 20,000 U.N. peacekeepers in Congo.

In May, Congo asked the United Nations to withdraw its peacekeepers and allow the country to take over its own security, saying the country has made significant progress in reducing threats to the safety of citizens.