The Rwandan military continues to provide weapons, fighters and other material support to the Congolese rebel group M23, which has stepped up its attacks on Congolese forces and civilians in the last few months, carrying out dozens of summary executions and rapes, a Human Rights Watch investigation has found.

The rebels have executed at least 44 people and raped at least 61 women in Congo (also known as the Democratic Republic of Congo or Congo-Kinshasa) since March, the international group has found. Its findings are based on more than 100 interviews with former M23 fighters and civilians living near the Rwandan border in eastern Congo where most of the recent fighting in the protracted war between the Congolese army and rebel factions has taken place.

In its interviews with M23 deserters, Human Rights Watch learned that the rebel group has been recruiting demobilized soldiers and civilians, including children, in Rwanda and training them to fight for its forces in Congo.

Rwandan army officers have also been seen at M23 bases, "leading training for new recruits and recruiting for the M23 in Rwanda," the group's report said.

Rwandan military 'directly supporting' rebels

M23 deserters reported seeing not just fighters being brought from Rwanda but also deliveries of weapons, ammunition, food, phone credit and other supplies.

"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," said Daniel Bekele, Africa director at Human Rights Watch. "This support is sustaining an armed group responsible for numerous killings, rapes and other serious abuses."

Human Rights Watch said recruitment of Rwandans has increased in recent months as M23 struggles to build up its forces after an internal split between rival factions that occurred in March. Several of the former recruits, some as young as 15, told the rights group that they were forcibly recruited or tricked into travelling to Congo with promises of jobs.

Congolese civilians accused by M23 of collaborating with Hutu militia groups have also been the target of forcible recruitment tactics, Human Rights Watch said.

Rape could be underreported

Women accused of being the wives of fighters for the Democratic Forces for the Liberation of Rwanda (FDLR), a Hutu armed group responsible for some of the killing and abuses carried out during the Rwandan genocide of 1994, are often the target of rape, the report said .

Although the group documented 61 cases of rape between March and mid-July, it said the social stigma around rape and the threat of reprisals against victims means the crime could be underreported.

"Most of the rapes occurred close to M23 positions, and some victims recognized the attackers as M23 fighters they had seen before," the report said. "The rapists frequently told their victims that they would be killed if they spoke about the rape or sought medical treatment."

More than 5 million dead

The Congolese army has been fighting various Rwandan-backed rebel factions for at least 15 years in a brutal war over the country's vast mineral resources that has claimed the lives of more than five million people so far and displaced hundreds of thousands of Congolese civilians.

M23 has emerged as the dominant rebel force in the past year, forming out of another Rwandan-backed group called the National Congress for the Defence of the People. With the backing of the Rwandan military, M23 has gained control of Rutshuru and Nyiragongo territories in North Kivu province in the east part of the county and in November 2012 briefly seized the key city of Goma on the Congo-Rwandan border, which has been the epicentre of the fighting that first erupted in 1998.

The M23 fighters retreated from Goma after the Congolese army agreed to pursue peace talks. A peace agreement endorsed by 11 African countries, including Rwanda and Congo, was signed in February but broke down when fighting erupted north of Goma in May and then again in July, Human Rights Watch said.

The group also uncovered killings, rapes and other abuses committed by the Congolese military and militia groups made up of ethnic Hutus and allied with the FDLR. Human Rights Watch alleges that Congolese army officers have supported the activities of the Hutu militias and that soldiers and officers have mistreated captured rebel fighters and civilians who support them.

UN says Rwandan support declining

The United Nations has recently authorized the deployment of a newly formed intervention force to carry out offensive operations against the armed groups operating in eastern Congo. The so-called Force Intervention Brigade is made up of 3,000 troops from South Africa, Tanzania, and Malawi. The unit falls under the broader 20,000-member UN peacekeeping force, dubbed MONUSCO, but has a stronger mandate to actively enforce peace by disarming combatants.

UN experts and other observers have long accused Rwanda of backing the M23 rebels, something the government of Rwandan President Paul Kagame has consistently denied.

A UN expert panel reported in June that Rwanda's support for M23 had declined in recent months, but Human Rights Watch said Rwanda's role continues to be key to the rebel group's operations.

"It does appear the support is more limited than it was last year, but what we have documented in terms of support is still quite significant," said researcher and report author Ida Sawyer.

M23 spokesman Kabasha Amani said Tuesday that Human Rights Watch is a "very partisan" organization and dismissed the group's findings.

"It's not a report, these are just rumours," Amani said. "We have grown used to this. It isn't the first time they've said these things."

With files from The Associated Press