Large explosion heard in central Baghdad

A large explosion rocked central Baghdad on Sunday and smoke was seen rising from inside the heavily fortified Green Zone, home to the US Embassy and Iraqi government. The cause of the explosion was not immediately clear and sirens were heard wailing across the Green Zone area. A US military spokesman confirmed the explosion, which occurred shortly before midday, but had no immediate details on what caused the blast. Insurgents have been known to target the area with mortar fire, although such incidents have fallen off in the last few months.