The rights organization said it determined from more than 100 interviews since March at least 44 people were summarily executed and 61 women and girls in eastern DRC were raped by March 23 Movement members.
Fighting in eastern DRC halted briefly after M23 forces gave up territory seized in an offensive last year. Fighting resumed mid-July and residents told the rights group the rebel campaign had support from Rwanda.
"Not only is Rwanda allowing its territory to be used by the abusive M23 to get recruits and equipment but the Rwandan military is still directly supporting the M23," Daniel Bekele, Africa director at Human Rights Watch, said in a statement Monday. "This support is sustaining an armed group responsible for numerous killings, rapes and other serious abuses."
Rwandan President Paul Kagame said allegations of support for DRC rebels like M23 were misguided. He said many of the problems in DRC require political, not military, solutions.
Human Rights Watch said many rebel elements in DRC are tied to the Rwandan genocide in the 1990s.