In their boldest and deadliest ambush yet, insurgents waylaid three minibuses carrying U.S.-trained Iraqi soldiers heading home on leave and massacred about 50 of them _ forcing many to lie down on the ground and shooting them in the head, officials said. Some accounts by police said the rebels were dressed in Iraqi military uniforms. The killing of so many Iraqi soldiers _ unarmed and in civilian clothes _ in such an apparently sure-footed operation reinforced American and Iraqi suspicions that the country's security services have been infiltrated by insurgents. A claim of responsibility posted on a Web site attributed the attack to followers of Abu Musab al-Zarqawi. Elsewhere, a U.S. diplomat was killed Sunday morning when a rebel-fired rocket or mortar shell crashed onto an American base near the Baghdad airport, the U.S. Embassy announced. Edward Seitz, 41, an agent with the State Department's Bureau of Diplomatic Security, was believed to be the first U.S. diplomat killed in Iraq since the war began in March 2003. A Bulgarian soldier was killed and two others were wounded in a car-bombing near Karbala, the Bulgarian Defense Ministry said. Karbala, a Shiite holy city south of Baghdad, has been quiet for months after U.S. troops routed Shiite militia there last spring. The Iraqi soldiers were killed on their way home after completing a training course at the Kirkush military camp northeast of Baghdad when their buses were stopped Saturday evening by rebels near the Iranian border about 150 kilometers (95 miles) east of Baghdad, Interior Ministry spokesman Adnan Abdul-Rahman said. There was confusion over precise figures, although the Iraqi National Guard said 48 troops and three drivers were killed.
