The massacre occurred overnight in the town of Oicha, in the Beni region, local administrator Donat Kibwana said.
The assailants were suspected members of the Allied Democratic Forces (ADF), an armed group blamed for hundreds of killings since 2014.
“They entered Oicha late at night, they pillaged and made off with farm animals. We lost nine people in the attack,” Kibwana said.
The toll was confirmed separately by military spokesman Mak Hazukay.
“The ADF got around our position and carried out their dirty work in eastern Oicha… there are nine civilians dead,” he said.
Local teacher Prospere Kasereka said “the ADF arrived in my area around 7.30pm. They started looting, smashing down doors and firing guns.”
He added: “I fled when they got in my house. I saw the bodies of nine inhabitants this morning.”
The ADF is a shadowy Islamist-rooted group that arose in western Uganda in 1995 under the leadership of Jamil Mukulu, a Christian turned Muslim.
Forced out of Uganda, it operates in the border area in the DRC’s North Kivu province, an area where other armed groups are also active.