At least 140 civilians were killed in July by Rwanda-backed M23 rebels in eastern Democratic Republic of Congo (DRC), according to a new report by Human Rights Watch (HRW). The rights group warned that the true death toll may exceed 300, a figure consistent with United Nations estimates.

The attacks took place in Rutshuru territory across at least 14 villages near Virunga National Park, despite renewed peace efforts, including a U.S.-brokered deal between Congo and Rwanda on June 27 and Qatar-hosted talks with the rebels.

Survivor testimonies gathered by HRW detail harrowing scenes. One woman recalled being forced to march with 70 women and children to a riverbank where M23 fighters opened fire. She survived after falling into the river before being shot. Another man said he watched from a distance as rebels killed his wife and four children, the youngest just nine months old.

Most of the victims were members of the Hutu community, while others were from the Nande ethnic group, HRW reported. The findings are based on interviews with 25 witnesses, medical staff, U.N. personnel, and local sources.

M23 has denied responsibility for the killings in the past and has not responded to the latest allegations.

In response, HRW urged the U.N. Security Council, the European Union, and national governments to expand sanctions and push for arrests and prosecutions. The organization also called on Rwanda to allow U.N. and independent forensic investigators access to areas under M23 control.