BENI - Eighteen people in eastern DR Congo's troubled region of Beni have been killed in a fresh attack by a notorious armed group, a local official said on Monday.

"There was an incursion in Apetina-Sana by the ADF last night," Beni administrator Donat Kibwana told AFP, referring to the Allied Democratic Forces militia.

"[They] hacked 18 civilians to death."

Apetina-Sana is 16 kilometers (10 miles) west of Oicha, the chief administrative town in the Beni region.

It is a point on the so-called Death Triangle, along with Mbau and Eringeti -- the worst-hit area for attacks.

ADF fighters 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, a civil society 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 also been demonstrations in the city of Beni, where local people accuse the U.N. peacekeeping force MONUSCO of failing to protect them.

The ADF began as an Islamist 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.