Suspected Ugandan rebels have killed four government soldiers in eastern Democratic Republic of Congo, the army said on Thursday.

Poor intelligence and lack of resources have hindered repeated offensives by Congolese and U.N. peacekeeping forces against the Allied Democratic Forces (ADF), a Ugandan Islamist group operating in northeastern Congo since the 1990s.

Wednesday’s attack targeted a Congolese military post east of the village of Opira, some 50 km (30 miles) north of Beni, said Lieutenant Mak Hazukay, the spokesman for local army operations. The U.N. mission said its force exchanged fire with the rebels but incurred no casualties.

The government and United Nations blame the ADF, which is active in the illicit timber trade, for the murders of hundreds of civilians near the town of Beni since 2014, although they estimate its size at no more than a few hundred fighters.

“Seven (soldiers) were gravely wounded,” Hazukay said. “Unfortunately, we lost four of them this morning.”

He said the bodies of two assailants had been recovered on the battlefield.

More than a decade after the formal end to regional conflicts in eastern Congo that killed millions of people, most from hunger and disease, dozens of armed groups are still exploiting its natural resources and attacking local people.

(Reporting by Aaron Ross; Editing by Makini Brice/Ruth Pitchford)