THIAM NDIAGA SIX members of a government-backed civilian militia have been found dead after an ambush in northern Burkina Faso, a local official and a military source said. The victims, killed on Thursday evening near the village of Dou, were members of the Homeland Defense Volunteers, a group of civilian fighters that receives funds and training from the government to help contain a violent Islamist insurgency. It was not yet clear who carried out the attack. Groups with links to al Qaeda and Islamic State operate inside the West African country. Five of the volunteers were ambushed while searching for…