Suspected members of the Allied Democratic Forces (ADF) attacked the town of Beu-Manyama in the Beni region on Sunday night, residents said.
"Three soldiers were killed in the ADF incursion and two others wounded," local leader Charles Endukadi told AFP, adding that several civilians were also injured.
Local civil society leader Kinos Katuo put the provisional toll at 13. Those killed included the local army commander, he added.
An army spokesman contacted by AFP refused comment but referred to a statement by army on Sunday which said troops had clashed with armed "terrorists" in the area, killing three.
The ADF — claimed by the Islamic State group as its Central African offshoot — is considered among the most violent of more than 120 armed movements active in the region.
It has been accused of slaughtering thousands of Congolese civilians and carrying out bomb attacks in neighboring Uganda.
Armed groups have roamed the volatile east of the Democratic Republic of Congo for decades, many of them a legacy of wars that flared in the late 1990s and early 2000s.
