Tutsi fighters loyal to renegade General Laurent Nkunda and Pareco Mai Mai militia, who had both signed a peace accord on Wednesday, blamed each other for the fighting early on Monday near villages 70 km (44 miles) west of the town of Goma.

Nkunda's National Congress for the Defense of the People (CNDP) and the Pareco Mai Mai faction were among 25 armed groups which had agreed to an immediate ceasefire in Wednesday's peace deal. The pact followed more the two weeks of negotations.

"This is a serious violation of the ceasefire that we've just signed," Seraphin Mirindi, a military spokesman for Nkunda, told Reuters on Monday.

Pareco Mai Mai spokesman Theophile Museveni blamed the attack on Nkunda's CNDP group.

The United Nations peacekeeping mission in Congo, which is trying to create buffer zones between the rival eastern factions as part of the ceasefire accord, said it could not confirm who had launched the first attack on Monday.