Three Tanzanian soldiers were killed and three others injured after a mortar shell landed near their camp in eastern Congo, where the Tanzanians are deployed under the banner of a regional bloc to help quell violence.

It remained unclear who was responsible for the attack on Saturday morning. It was reported on Monday by the regional bloc, the Southern African Development Community, or SADC.

SADC also said in a statement that a South African soldier had died while being treated for undisclosed “health challenges.” It sent condolences to the Tanzanian families of the victims. The bloc’s peacekeeping mission was launched in December as a longstanding group of UN peacekeepers known as MONUSCO gradually pulls out of Congo.

Eastern Congo is rich in minerals, with various armed groups battling for control of resources. The most prominent of them is the M23, which has caused the displacement of hundreds of thousands of people in North Kivu province in recent years. The M23 was most recently threatening to take Goma, the largest city in the region.

President Felix Tshisekedi of Congo blames neighbouring Rwanda for providing military support to the M23, an allegation Rwandan officials no longer deny after the US earlier this year described the group as backed by Rwanda.

In February, the US urged Rwanda to withdraw its troops and surface-to-air missile systems from eastern Congo, and urged both Rwanda and Congo to pull from the brink of war after a dramatic buildup of weapons at the border.

Rwandan President Paul Kagame told reporters on Monday that the M23 deserve to be supported because they are struggling for the rights of Congolese Tutsis who “have been denied their rights as citizens of that country.”

“They are called Tutsis of Rwanda,” he said, responding to a question about whether Rwanda actively supports the violent armed group. “Those who accuse us, I would ask them why they actually don’t support M23 themselves.”

Rwandan authorities oppose the deployment in eastern Congo of peacekeepers from SADC, saying they are interfering in an internal problem that only Congolese can solve. Rwandans have warned that the deployment of SADC peacekeepers alongside Congolese troops is tainted because the Congolese military had recruited members of a rebel force led by perpetrators of the 1994 genocide in Rwanda.

Kagame said Monday in Kigali that he had spoken with South African President Cyril Ramaphosa, who was in Rwanda on Sunday to attend the official commemoration of the 30th anniversary of the genocide. Kagame did not give details of their talks.

Conflict in large areas of eastern Congo has displaced more than 7 million people, according to the U.N., making it one of the world’s worst humanitarian crises.

• An AP report