Suspected Islamist rebels have killed about 15 people in east Congo, an official said on Wednesday, the latest in attacks causing anger at perceived inaction of the army and U.N. troops.

The raid occurred overnight in the village of Maleki, near the city of Oicha in a forested region near the Ugandan border, said Donat Kibwana, the administrator of Beni territory.

Kibwana blamed the attack on the Allied Democratic Forces (ADF), a jihadist rebel group originally from Uganda that has operated for decades in Congo. They have killed at least 80 people in 14 raids since the army launched an operation against them late last month, according to U.N figures.

“It is deplorable what I just saw at the morgue of the general hospital of Oicha. The attackers massacred civilians with knives. I counted 15 dead,” Kibwana said.

Several previous ADF attacks have been claimed by Islamic State, but the extent of their relationship remains unclear.

Recent attacks sparked protests in the city of Beni, 20 km (12 miles) south of Oicha, driven by accusations that the army and United Nations are not doing enough to protect people.

Protesters burned down the mayor’s office and damaged U.N. facilities on Monday, forcing some health workers helping to combat an Ebola epidemic into lockdown and others to leave.

At least four people have died during protests in Beni and nearby Butembo this week. On Wednesday the protests spread to Goma, the regional capital, where activists have called for a two-day strike starting on Thursday.

One protester was allegedly killed during an exchange with U.N. peacekeepers in Beni on Monday, the United Nations said, adding that it would open an investigation.

The U.N. peacekeeping mission said in a statement on Wednesday that it would be unable to end the ADF’s violence if its forces were under attack from local people.