A suicide car bomb exploded at a police checkpoint in Iraq's volatile Diyala province Sunday, killing at least 15 people, including seven policemen, a security official said. Police Major Hassan al-Kurawi said another 20 people were wounded in the attack, which took place east of the provincial capital Baquba hours after Iraq's cabinet approved a wide-ranging military pact that would have all US troops withdraw by the end of 2011.