GOMA, D.R. Congo — Unidentified assailants stabbed 12 patients in their hospital beds in the restive D.R. Congo city of Goma, with fears it was the work of Ugandan rebels, officials said on Tuesday.

Three of the victims were seriously hurt in the knife rampage overnight Sunday-Monday in two health centers in the Goma district of Mbosho, provincial health minister Martial Kambumbu said.

“It is the first time we have seen patients being stabbed in health facilities in Goma,” said Etienne Kambale, civil society rapporteur in North Kivu province, of which Goma is the capital.

“It is surprising. We are wondering if it was the ADF who have turned up in Goma, because this is the way they killed people in Beni.”

Government forces last month launched an offensive in Beni against the Allied Democratic Forces (ADF), one of a number of armed groups that hold territory in the eastern DR Congo and are battling for control of the region’s rich mineral resources.

Beni lies about 250 km north of Goma.

Congolese authorities and the UN mission in DR Congo, MONUSCO, accuse the ADF of killing more than 700 civilians as well as combatants in the Beni region since 2014.

The group is also blamed for the killing of 14 UN peacekeepers last month, the biggest single such loss in 25 years.