KINSHASA: Seven Congolese soldiers were killed on Thursday in a surprise attack by heavily armed assailants in Congo's restive northeast, military and local sources said, in what appeared to be an operation by Ugandan Islamist rebels.

Attackers wielding guns and bladed weapons targeted a camp run by the Congolese army (FARDC) near the town of Mbau, about 12 km (7 miles) north of the territorial capital of Beni, according to one military source.

"There were seven deaths among the FARDC and four wounded though we tried to defend ourselves," the military source said.

The Center of Study for the Promotion of Peace, Democracy and Human Rights (CEPADHO), a local activist group, gave the same figures. It said two civilians and four assailants had died in the attack, which culminated in a firefight lasting more than two hours.

CEPADHO blamed the attack on the Allied Democratic Forces (ADF), a Ugandan Islamist group active near Beni.

Local activists say the group has been responsible for a spate of overnight massacres of civilians since last October that have killed more than 400 people, despite operations against it by Congolese forces and U.N. peacekeepers.

Mak Hazukay, deputy spokesman for the army's operations in the area, denied that any Congolese soldiers had been killed in the attack. He said one soldier was wounded while six unidentified assailants were killed.