Dark smoke rose from the US-protected Green Zone early Sunday after it was targeted by a series of rockets or mortars. Some 10 blasts were heard in the sprawling area in central Baghdad starting shortly before 6 a.m., and helicopters buzzed overhead. The US public address system there warned people to "duck and cover" and to stay away from windows. US officials did not respond to a request for comment about the attack. Last month, the US military blamed what it calls Iranian-backed Shiite militias for a series of deadly rocket attacks in Baghdad. Those included one that struck Camp Victory, the main US military headquarters, and an Iraqi housing complex on the capital's southwestern outskirts on Feb. 18, killing at least five people and wounding 16, including two US soldiers. The military said the extremists were among factions that have broken with radical Shiite cleric al-Sadr and refused to follow his cease-fire order. Iran denies allegations that it is stoking the violence. Al-Sadr has extended the cease-fire through mid-August.