Human Rights Watch says a rebel group in eastern Democratic Republic of Congo has committed widespread war crimes, including rapes, killings and torture, abduction and recruitment of children as soldiers.

In a report issued Monday, the U.S.-based rights organization says the group March 23 Movement, known as M23, is committing a horrific trail of new atrocities in eastern Congo. It says the group has executed 33 of its own fighters for trying to desert, and that 15 civilians have been killed in rebel territories since June.

United Nations experts say M23 rebels are receiving support from neighboring Rwanda, which officials in Kigali deny.

Human Rights Watch based its findings on interviews with close to 200 Congolese and Rwandan victims, family members, witnesses, local authorities and current or former M23 fighters.

The M23 armed group consists of soldiers who participated in a mutiny from the Congolese national army in April and May. The group's senior commanders have a history of serious abuses against civilians.

Two of the most notorious are Bosco Ntaganda, who is wanted by the International Criminal Court on charges of war crimes and crimes against humanity, and Sultani Makenga, who is implicated in the recruitment of children and several massacres in eastern Congo.

The six-month conflict between the M23, the Congolese army and various other armed groups in Congo's eastern hills has forced at least 220,000 civilians to flee their homes.

International efforts to stop the violence have stalled.