The victims were shot dead or hacked to death
Rebels went on a rampage in villages around the northeastern DR Congo city of Beni at the weekend, killing at least eight people and abducting many more, local officials said.
The first attacks occurred overnight Friday in the villages of Mbingi and Mapasana.
"There we had four people killed, seven motorbikes and several houses torched, and the kidnapping of several people," said Kinos Katuo, the head of a civil society body.
He said the victims were shot dead or hacked to death.
Sunday morning the rebels of the Allied Democratic Forces (ADF) attacked the nearby village of Mangazi, he said, noting that a rebel was killed as the army repelled the assault.
The rebels moved on to the villages of Matekelambi and Mabuo, where the death toll stands at four, with "many others missing," Katuo said.
No military source was available Sunday to confirm his account.
Nicolas Kikuku, mayor of the nearest city, Oicha, said "It's true that the enemy is present in this area."
Of the more than 100 armed groups active in eastern DRC, the ADF is said to be the most deadly.
The so-called Islamic State group (IS) has designated the ADF its Central Africa Province, or ISCAP.
The United States officially linked the ADF to IS in March 2021.
The government in Kinshasa declared a state of siege in North Kivu and neighbouring Ituri in May in an effort to stop the activities of armed groups, including the ADF.
Military and police officers have replaced civilian authorities as heads of these provinces.