The ADF was formed in Uganda in the 1990s before moving over the border and has been blamed for killings in the DRC, too.

Other villagers fled but might have drowned as they tried to cross the Lamia River into Uganda, Maurice Mabele Musaidi told Reuters news agency.

“There are still people missing,” he said.

Musaidi and a spokesperson for the DRC army said the attack in Beni territory’s Watalinga chiefdom was carried out by the Allied Democratic Forces (ADF), an armed group based in the eastern DRC that has pledged allegiance to ISIL (ISIS).

The ADF was formed in Uganda in the 1990s before moving over the border and has been blamed for thousands of killings in the last decade across both countries.

In June, ADF fighters killed 42 people, including 37 students, at a high school in western Uganda near the DRC border in what was the country’s deadliest attack in more than a decade. In November, the Ugandan army said it captured the head of an ADF unit known simply as “Njovu” and killed six of his men in a raid.

The DRC’s army said it killed at least six of the attackers on Sunday night, without going into detail on the operation. Army spokesperson Antony Mualushayi put the civilian death toll at 11, though he said that figure was provisional.