Militants bombarded Baghdad's Green Zone with rockets on Sunday, taking advantage of the cover of a blinding dust storm to launch one of the heaviest strikes in weeks on the fortified compound, Reuters reported.
The strikes appeared to defy a renewed call for a ceasefire by Shi'ite cleric Moqtada al-Sadr, which has seen many of his masked gunmen leave the streets of the Sadr City slum where they hold sway in eastern Baghdad.
Reuters correspondents heard the missiles whistling overhead and exploding inside the heavily fortified government and diplomatic compound on the west side of the Tigris River in Baghdad. Sirens wailed, ordering people to take cover.
Iraqi police said eight missiles or mortars had hit the Green Zone and another 14 fell in other parts of the Iraqi capital before nightfall in several quick bursts, killing two people and wounding 20.
"The Green Zone has received several rounds of IDF (indirect fire) but I can't say more than that," U.S. embassy spokesman Armand Cucciniello said. "The duck and cover alarm sounded and people ran out for cover."
Several more missiles were fired late on Sunday evening but it was unclear if there were any casualties.
The United States blames rogue elements of Sadr's Mehdi Army militia for firing the rockets. It accuses neighbouring Shi'ite Iran of supplying the weapons and says some were made as recently as last year. Iran denies the accusations.
Militiamen have fired 700 missiles and mortars over the past month in Baghdad, but U.S. forces had said they believed they had reduced the fighters' ability to strike the Green Zone by occupying the part of the Sadr City slum closest to it.
U.S. forces normally respond rapidly to missile firings with helicopter strikes, but those are impossible in dust storms.
The U.S. military said it killed six militants in air strikes overnight in Sadr City before the weather turned bad in the afternoon. Iraqi police and hospital sources said 10 people were killed and more than 40 wounded overnight there.
"I would like to emphasise that these are not 'violent' clashes, at least not in our definition. They are not protracted gunfights," said U.S. military spokesman Lieutenant-Colonel Steven Stover. "While attacks continue there have been less."
Inside Sadr City, a Reuters reporter said the black-masked fighters who have long prowled the streets were keeping a low profile in response to Sadr's call for them to observe a truce.
"This morning, the Americans entered on foot from the Jamila area. We could have hit them, but we have orders to defend the city against the occupiers but not inside the city," said Abu Jassim, a Mehdi Army street commander. Outside Sadr City a Reuters reporter saw fighters planting a roadside bomb.
The government's confrontation with Sadr's Mehdi Army began a month ago when Shi'ite Prime Minister Nuri al-Maliki launched a crackdown on militias in the southern city of Basra.
Despite initial setbacks, the Basra campaign has since proved largely a success, with government troops taking control of neighbourhoods once regarded as militia strongholds.
In Sadr City, the cleric's main Baghdad stronghold, U.S. forces have advanced only into a small portion of the slum to put 107 millimetre missiles out of range of the Green Zone.
Fighting and air strikes in the district over the past month have killed hundreds. Food prices have skyrocketed and residents say they feel under siege. Many schools have shut.
Major-General Qassim Moussawi, Iraqi military spokesman for security in the capital, acknowledged civilian casualties were inevitable in fighting in a crowded slum.
"The area of this (Sadr) city is around 25 square kilometres (10 square miles) with an estimated population of 3 million. This means if a bullet is shot, it will hit a person," he said.
Um Aziz is an elderly woman whose three daughters and a son were killed when the roof of her house collapsed because of the force of an explosion nearby. She cursed U.S. forces.
"I don't want any reparations from the government. I want my revenge from God," she said outside her ruined home, wearing bandages from her own injuries and a broken leg.
"Let the Americans listen: If they kill all the men, we will fight them. We: the women and the children. And if they take our weapons we will fight them with stones and knives."
In a sign of progress towards national reconciliation, Maliki met Sunni Arab Vice President Tareq al-Hashemi to discuss the eventual return of the main Sunni Arab bloc to Maliki's government, which it quit last year.