The fortified Green Zone in Iraq's capital has again come under attack by rockets or mortars. A thick cloud of smoke was seen over the zone Friday about 2:30pm, shortly after two rounds hit. It was the day's first attack on the area. The Green Zone houses the US Embassy and much of the Iraqi government and has come under fire with regularity since Easter Sunday. At least two American civilians have been killed in the attacks. Several others have been injured, some seriously, US officials have said.