Three American soldiers were killed and one was wounded in two separate attacks in Iraq on Saturday, the U.S. military said. The deadlier of the attacks happened in the morning when a man dressed in an Iraqi army uniform opened fire at U.S. soldiers while they were conducting a training session for Iraqi forces at a military base on the outskirts of the volatile northern city of Mosul, Col. Barry A. Johnson, spokesman for the commander of U.S. forces in Iraq, said. The attacker killed two U.S. soldiers and wounded a third before he was shot dead, Col. Johnson said, declining to give further details because the attack was under investigation. The wounded soldier was flown to a field hospital at the Balad air base north of Baghdad for treatment, he said. A third U.S. soldier was killed in a separate attack in central Iraq, while "conducting operations," according to a military statement. The U.S. Army's central division includes Baghdad and the western Anbar Province. Col. Johnson said he couldn't discuss the second attack.