The Rwanda-backed rebel group M23 has denied involvement in recent massacres in eastern Congo. A report by Human Rights Watch, released Wednesday, accused M23 of killing over 140 civilians.

Despite a peace process, attacks were carried out in more than a dozen villages last month, Human Rights Watch says.

M23 denies Human Rights Watch findings linking it to massacres in eastern Congo, as rights groups cite mass killings and the U.S. urges U.N. action.