Suspected Islamist rebels killed at least 10 civilians in an attack on Friday near the city of Beni in eastern Democratic Republic of Congo, local authorities and a U.N. source said.

The assailants fired guns at people working in fields in Mulekera commune outside Beni, Mulekera Mayor Ngongo Mayanga said on Saturday.

Seven bodies have been collected so far, including those of three women, with a further five victims reported elsewhere, he said.

“Certainly there are other bodies that we will find as the search continues,” he said by phone, blaming the Allied Democratic Forces (ADF) rebel group.

A source in the U.N. peacekeeping mission in eastern Congo said 10 people were killed.

The ADF originates from neighbouring Uganda. Now based in eastern Congo, it has pledged allegiance to Islamic State and mounts frequent attacks, further destabilising a region where many militant groups are active.

A witness to the latest attack said he was working in a field when he heard the sound of bullets shortly after parting from his daughter-in-law.

“My daughter-in-law went in the opposite direction, but unfortunately that’s when she was killed,” he said, describing how he fled into the forest and spent the night there out of fear of the attackers.

Decades of conflict between the army and numerous rebel groups have destabilised eastern Congo and fuelled a long-running humanitarian crisis.

Attacks have intensified over the past year and the number of people displaced by the violence stood at 7.1 million at the end of March, according to the U.N. humanitarian agency OCHA.