Insurgents fired a mortar Sunday into the heavily fortified Green Zone, home to the U.S. Embassy and Iraqi government, but there were no casualties.

The loud explosion rocked central Baghdad shortly before midday and sent a cloud of smoke rising from within the Green Zone.

U.S. military spokesman Maj. Tim Keefe said no casualties or damage were caused.

Insurgents have been known to target the area with mortar fire, although such incidents have declined in the last few months.