Three of the victims were seriously hurt in the knife rampage overnight Sunday-Monday in two health centres in the Goma district of Mbosho, provincial health minister Martial Kambumbu told AFP.
"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."
Beni lies about 250 kilometres 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.