Systematic and brutal attacks by militants in the Democratic Republic of Congo over the last 18 months may amount to war crimes, the United Nations said on Monday.

The Allied Democratic Forces (ADF), a Ugandan armed group operating in eastern Congo, have killed more than 1 000 civilians since the start of 2019, according to a report by the UN Joint Human Rights Office (UNJHRO).

“In the majority of cases, the means and the modus operandi of the attacks indicate a clear intention to leave no survivors. Entire families have been hacked to death,” it said.

The attacks “may amount to crimes against humanity and war crimes”, it said.

The ADF has operated in Beni territory, North Kivu province, for more than three decades, but the level of violence increased sharply last year following military campaigns against them, the report said.

Even by the standards of eastern Congo, where militias routinely attack civilians as they vie for territory and natural resources, the repeated massacres by the ADF of defenseless villagers have been particularly vicious.

Several have been claimed by Islamic State, although researchers and analysts say there is a lack of hard evidence linking the two groups.

Last October, President Felix Tshisekedi sent 22 000 troops, including special forces, to oust the ADF from their bases in the dense forests near the Ugandan border.

As a result of the army offensive, combatants dispersed into small groups and fled into other areas, especially into neighbouring Ituri province, the report said.

However, the violence has continued, with ADF fighters routinely massacring civilians and ambushing army soldiers. They have burned down entire villages, destroyed health centres and schools, and abducted men, women and children, UNJHRO said.

State security forces also committed serious human rights violations during operations against the ADF, the report said, including killing 14 civilians and injuring 49 others in the last eight months.