Life in areas controlled by the M23 rebels in eastern Democratic Republic of Congo is one of daily suffering and fear. Families worry their children will be forced to the frontlines, their wives, sisters, and mothers might be raped in their fields, or their brothers and husbands killed for being “on the wrong side.”

Just in the last two weeks, M23 fighters executed two local chiefs, shot and stabbed to death a boy, and shot dead at least three other men. Their shelling of populated neighborhoods in and around Goma killed at least seven civilians and wounded more than 40. A 16-year-old girl was killed while bathing when a mortar landed outside her home. A 14-year-old boy was killed when a mortar hit his home as he slept. Another mortar landed on a school, crushing to death a child playing.

Since April 2012, the rebels have committed widespread war crimes, including summary executions, rapes, and forced recruitment of children.Yet Rwanda has supplied them with weapons and ammunition, provided them new recruits, and backed them with military forces. Other armed groups and Congolese soldiers have also committed serious abuses.

Intense fighting between the M23 and the Congolese army resumed on August 21, 2013. This time, the United Nations’ peacekeeping force in Congo, including its new intervention brigade, supported the Congolese army with attack helicopters, artillery fire, and ground troops. The M23 retreated on August 30, ceding to the Congolese army strategic positions north of Goma.

Senior UN officials told us that only a regular army could withstand such sustained, heavy fire for as long as it did, and that it was clear the M23 were receiving daily reinforcements. Villagers who live along the Congo-Rwanda border told us they saw large-scale movements of troops and weaponry from Rwanda into Congo. Some said they were forced to carry ammunition from Rwanda to M23 military positions in Congo.

There’s a new opportunity to end the rampant abuses. The UNforces have shown a willingness to take action to protect civilians. The United States has publicly called on Rwanda to cease support to the M23. The UN secretary-general called Rwandan President Paul Kagame to urge restraint, and the UN says it has “consistent and credible reports” of Rwandan troops entering Congo in recent days. A visit by the UN,US, European Union, and African Union special envoys to the Great Lakes is to start on Wednesday. Heads of state of the International Conference of the Great Lakes Region, which includes Rwanda and Congo, are to meet on Thursday.

This is the moment to use all diplomatic clout possible to stop further atrocities against civilians by the M23, and to call on Rwanda to end all support to the rebels and use its influence to ensure any agreement the M23 accepts does not reward war criminals. If not, Kigali should face further international action, including targeted sanctions and military aid cuts.