A Sunni Arab tribal chief and four members of his family have been shot dead as they slept in their Baghdad home by gunmen wearing Iraqi army uniforms.
The Defence Ministry has denied that Iraqi troops were responsible, saying the attack must have been carried out by terrorists in disguise.
It follows the discovery last week of more than 170 malnourished and beaten prisoners – many of them Sunni Arabs – in a bunker belonging to the Shi’ite Arab-dominated Interior Ministry.
Together the incidents have raised fears that Iraq is heading for civil war. Tensions between Sunni and Shi’ite Arabs are already running high in the run-up to parliamentary elections on December 15.