Allied Democratic Forces, a militia originally from neighbouring Uganda, has killed more than 200 people since the army launched an offensive against the militia on October 30, according to a toll compiled by civil society groups.
Militants killed 20 people, most of them hacked to death, in Democratic Republic of Congo's eastern Beni region in the latest attack by an armed group blamed for massacres that have sparked angry protests.
Local officials said militants from the Allied Democratic Forces, a militia originally from neighbouring Uganda, on Sunday attacked Apetina-Sana west of Oicha, the chief administrative town in Beni region.
"There was an incursion in Apetina-Sana by the ADF last night," Beni administrator Donat Kibwana told AFP.
"(They) hacked 18 civilians to death."
Local officials later found two more bodies during a search after the attack, bringing the total to 20.
Triangle of Death
Apetina-Sana is part of the so-called Triangle of Death, along with Mbau and Eringeti – the worst-hit area for attacks by the ADF.
ADF militants have killed more than 200 people since the army launched an offensive against the militia on October 30, according to a toll compiled by civil society groups.
The toll has sparked anger over the authorities' response.
"The authorities were tipped off on Sunday evening about the presence of suspicious men west of Oicha," said Teddy Kataliko, an activist in Beni.
"We continue to ask the DRC armed forces to launch operations on the western side as well, to save civilians."
There have been demonstrations in the city of Beni, where local people accuse the UN peacekeeping force MONUSCO of failing to protect them.
The ADF began as a rebellion hostile to Ugandan President Yoweri Museveni.
It fell back into eastern DRC in 1995 and appears to have halted raids inside Uganda. Its recruits today are people of various nationalities.
Attack in Irumu district
In a separate incident in eastern DRC on Monday, "armed bandits" attacked a base used by a Chinese-owned gold mine, killing four people, the military said.
The raid happened in Irumu district in the northeastern province of Ituri, said Lieutenant Jules Ngongo, the army's provincial spokesman.
Two soldiers, a policeman and a driver for the mine were killed, he said.
"The assailants have not been completely identified but they must be armed bandits who look for supplies during the year-end festivities," Ngongo said.