Members of the Allied Democratic Forces (ADF), an Islamist-rooted militia with its origins in Uganda, killed the civilians using machetes, Beni region administrator Donat Kibwana told AFP.
“Teams have been mobilised to recover the bodies and bring them back for dignified funerals,” he said.
The victims were farmers and included 13 women, said Noella Katsongerwaki, Beni’s civil society president.
Dozens of armed groups have troubled the DR Congo’s restive east for decades despite a UN peacekeeping presence, but recent attacks have been blamed on the ADF.
More than 100 people have died in assaults blamed on the group since November 5.
The latest incident came a day after six civilians were killed in an attack in the eastern city of Beni.
DR Congo forces launched operations against the militia in the eastern region at the end of October.
The ADF has retaliated by carrying out massacres, in an apparent bid to discourage civilians from helping the military.
Mounting anger over militia violence has sparked demonstrations in the eastern city of Beni, where local people accuse the UN peacekeeping force MONUSCO of failing to protect them.
MONUSCO has said it will carry out joint operations with the Congolese army to crackdown on the ADF.
MONUSCO, one of the biggest UN peacekeeping operations in the world, today comprises more than 16,500 military personnel and observers, 1,300 police and at least 4,000 civilians.
But it has struggled to make progress in a vast country beset by armed groups as well as an Ebola epidemic, poverty and poor governance.