Special report: Tension escalates in Iraq 　　

    BAGHDAD, May 2 (Xinhua) -- A U.S. unmanned spy plane crashed in southern Iraq during a mission on Friday, the U.S. military said.

    "An Air Force MQ-1 Predator crashed in southern Iraq at approximately 4 a.m. local time (0100 GMT) today," a military statement said.

    The medium-altitude, long-endurance, remotely piloted aircraft was launched from Ali Base located near Nassriya City, 375 km south of Baghdad, the statement said.

    The aircraft was on an armed reconnaissance mission, the military said without details about how and where exactly the aircraft went down.

    The military said a board will be convened to investigate the incident.

    The U.S. troops heavily depend on drone aircraft to provide close aerial support during clashes with militiamen.