The violence broke out in the town of Eringeti in North Kivu province, AFP reports. Regional official Amisi Kalonda blamed the most recent deaths on Alllied Democratic Forces (ADF) rebels.
The ADF, a rebel group dominated by Ugandan Muslims and thought to be allied with Al-Shabab, poured into the town December 24.
"Yesterday, they killed 10 civilians. Twelve other bodies were found (Sunday) in the surrounding villages," Kalonda said. The victims had been killed with knives or machetes, he said, an ADF hallmark.
A Catholic priest in the area told AFP there had been 27 deaths and the toll could rise "if bodies are found in the forest" surrounding the town.
While officials are blaming the ADF, other reports suggest that other groups, including elements of the Congolese army, may have taken part.
A Congolese army spokesman confirmed the attacks, calling the civilian toll "very heavy," but noting that the army had "killed four ADF rebels," according to Al Jazeera.
Hundreds have been hacked to death in the area around Beni, the regional hub of North Kivu, since 2014, with Congolese authorities and the UN mission in the region unable to do much to protect civilians.
A source told AFP another attack was underway the evening of December 25 in the town of Oicha. An army spokesman would only say that troops were engaged in an operation in the area.
The latest bloodshed comes at a moment of political tension in the country. President Joseph Kabila and his supporters have been engaged in a standoff with opponents over his refusal to call an election or step down, despite his term ending December 20. Kabila has been in power since 2001.
On December 24, opposition leaders announced that Kabila had agreed to step down by the end of 2017 and that the constitution would not be altered to allow him to run for a third term, but not before more than two dozen were killed and many more arrested during demonstrations earlier in the week against Kabila and his refusal to let go of power.
The final deal has apparently not yet been signed.