US military officials are worried about the increasing use of chemical bombs in Iraq.

A car bomb and a suicide attacker killed at least 11 people in Baghdad today as militants showed increasing defiance to a major security operation in the Iraqi capital.

A string of bombings killed 10 people in the Baghdad area today and the US announced a marine had died in fighting west of the Iraqi capital.

Militants struck back in their first major blow against a US-led security clampdown in Baghdad with car bombings that killed at least 63 people and left scores injured.