The US military says a rocket attack on the US-protected Green Zone has killed two American soldiers and wounded 17. A military official says the casualties occurred when at least two rockets struck the sprawling area in central Baghdad. The official spoke on condition of anonymity for lack of authorization to release the information. The Green Zone has faced frequent attacks amid fierce clashes between Shi'ite militia fighters and US-Iraqi forces. Nobody has claimed responsibility for Sunday's attack, but the military has in the past blamed Iranian-backed rogue Shi'ite militia groups for the attacks.