More than 80 civilians were killed in a late night attack by the armed group CODECO on a cluster of villages in eastern Democratic Republic of Congo earlier this week, UN peacekeeping mission MONUSCO said on Thursday.

The new death toll far exceeds a previous estimate of at least 51 people killed, which local authorities shared immediately after the attack took place overnight on Monday in Djugu territory, Ituri province.

MONUSCO said it had deployed peacekeepers to counter the assault as quickly as possible, but said that the militants' use of bladed weapons rather than louder firearms had delayed its response.

Once the peacekeepers were on the ground, the group "had unfortunately already killed more than 80 civilians, set homes ablaze, and spread panic among the population," the mission said in a statement.

CODECO is one of a myriad of militias fighting over land and resources in eastern Congo. It has frequently targeted displacement camps, which have ballooned since recent advances by Rwanda-backed M23 rebels.

M23 has been inching south since they seized eastern Congo's largest city of Goma at the end of last month, with some 3 000 people killed in the days preceding the city's capture, according to UN figures. Their advance from North Kivu province into South Kivu province threatens to trigger a humanitarian catastrophe, local officials say.