Four U.S. Marines have been killed in fighting in western Iraq, the American military announced Saturday, taking the number of U.S. personnel killed during a weeklong operation against insurgents to nine. The four latest Marines to die were killed Wednesday when their troop transporter was struck by a bomb near Karabilah, a village close to the Syrian border, during Operation Matador, the Marines said in a statement. The Associated Press quoted the statement as saying Marines commanders estimate more than 100 insurgents and foreign fighters have been killed during the operation, which is aimed at allies of Jordanian-born militant Abu Musab al-Zarqawi. At least 1,617 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.