Militiamen took advantage of a heavy sandstorm in Baghdad on Sunday firing volleys of rockets or mortar rounds, with at least 10 hitting the heavily fortified Green Zone, an Iraqi official said.
"At least 10 rockets or mortars hit the Green Zone," the interior ministry official said, adding it was not immediately clear if these had caused any casualties.
The projectiles triggered alarms and sent US embassy staff scurrying for cover, an embassy official said.
US and Iraqi military commanders say around 700 rockets or mortar bombs have been fired from various locations in Baghdad in the past month, particularly from Sadr City, the East Baghdad bastion of the Mahdi Army militia of radical anti-American cleric Moqtada Al Sadr.
Of these, 114 have hit the Green Zone where the Iraqi government and US embassy are based, killing two US soldiers, two US embassy personnel and two Iraqi guards.
Those firing the rockets are often identified by US surveillance aircraft that alert helicopters, which deploy Hellfire missiles against the attackers.
However, with the sandstorm reducing visibility, helicopters were unable to take off allowing the militiamen to escape after firing the deadly missiles.
General Abud Qanbar Hashim, Iraqi commander of Baghdad Operations Command, last week said 82 people had been killed and 476 wounded in rocket and mortar-round fire in Baghdad since March 25, much of it coming from Sadr City.
Iraqi army spokesman Major General Qasim Atta told a news conference in Baghdad on Sunday that most of the rockets fired were Iranian-made.
"We have found many Iranian-made weapons – Katyusha and Grad rockets, and smart roadside bombs and smart bombs. We have also seized some documents and identified some people," Atta said, without elaborating.
Clashes between militiamen and US-Iraqi forces in Sadr City, which the American military says are aimed at preventing the rocket fire, have killed more than 400 people in the past month, according to an AFP tally based on reports by Iraqi and US officials.