KINSHASA (Reuters) - Rebel fighters killed at least eight civilians in eastern Democratic Republic of Congo before fleeing when Congolese troops arrived, local sources said, in a region where a spike in ethnic violence has halted some aid deliveries.

Hundreds of civilians have died over the past year in inter-communal violence and a series of massacres by armed groups in Congo’s North Kivu province, which borders Rwanda and Uganda.

Lawless eastern Congo is plagued by dozens of armed groups that prey on the local population and exploit mineral reserves. Millions died there between 1996 and 2003 as regional conflict caused hunger and disease. The recent increase in violence has prevented aid from reaching vulnerable populations.

On Sunday, an ethnic Nande militia, the Mai-Mai Mazembe, killed at least seven civilians in the town of Kibirizi before the troops arrived, local activist Innocent Gasigwa said.

Gasigwa said the attack appeared to be revenge against the Rwandophone community in Kibirizi. Rebels from the Rwandophone Hutu ethnic group were suspected of killing at least seven civilians last month in an attack targeting the town’s Nande residents.

He said an ethnic Hutu militia, the Nyatura, had also killed a man on Sunday in the nearby town of Nyanzale who was suspected of belonging to Mai-Mai Mazembe.

Local army spokesman Captain Guillaume Djike said the attacks near Kibirizi and Nyanzale were both the work of the Nyatura and that they killed at least 11 people with firearms and machetes and burned down dozens of houses.