Suspected militants shelled Baghdad's protected Green Zone on Saturday in the first such bombardment in more than three months.
The back-to-back strikes reverberated across the Tigris River to a popular promenade, sending families packing up from fish restaurants and abruptly halting a party at a club.
Violence across Iraq remains sharply down compared with past years, but attacks and bloodshed have edged up in recent weeks and brought worries that it could slow the return of nightlife and commerce to parts of Baghdad.
The U.S. military said the Green Zone was hit by two "indirect fire" rounds — which typically means either rockets or mortars — but there were no casualties or damage reported.
A police official says the rounds were fired from predominantly Shiite eastern Baghdad. The official spoke on condition of anonymity because he was not authorized to speak to media.
The attack came during a light sandstorm, which prevents helicopter patrols and gives militants cover.
The Green Zone was last targeted by rockets or mortars on Jan. 15, leaving one person injured. The attacks are usually blamed on Shiite militias. The area contains the U.S. and British embassies and key Iraqi government offices.
West of Baghdad, Iraqi forces launched raids into an industrial zone in Fallujah where authorities fear Sunni insurgents could be seeking to regain footholds in areas they once controlled.
But the offensive into the district of factories and workshops found no clear evidence that al-Qaida in Iraq or its allies had re-established a major presence in Fallujah, said the city's police chief, Col. Mahmoud al-Issawi.
He said police and military units found only small stockpiles of buried weapons and explosives. No arrests were made during the all-day sweep.
Security forces, however, have sharply stepped up their guard against the possible return of extremist factions to areas that have been relatively calm.
Fallujah, about 40 miles west of Baghdad, was a hub for al-Qaida in Iraq and other insurgent factions before they were mostly driven out by a Sunni tribal uprising and U.S.-led campaigns more than two years ago.
There are worrying signs of violence returning.
On Thursday, a suicide bomber struck an Iraqi military base in Habbaniyah near Fallujah. The blast injured at least 38 Iraqi soldiers — and was the fourth major attack against Iraqi security forces this month.
The industrial zone in Fallujah was once a center for insurgent bomb-making and rocket production. Streets were sealed off before Iraqi police and military units swept in, said al-Issawi.
In a separate operation, U.S. Marines joined Iraqi security forces in a hunt for weapons caches near Karmah village east of Fallujah, the U.S. military said.
Gunmen in Baghdad, meanwhile, killed a police intelligence official working for the Interior Ministry, said police and hospital officials.
The drive-by shooting occurred as Col. Haider Hadi Fadhil stopped his car at the gate of his house in a Shiite neighborhood in eastern Baghdad. The attack also wounded Fadhil's brother, said the officials, who spoke on condition of anonymity because they were not authorized to speak to release the information.
In southern Iraq, Iraqi security forces said they captured four suspected insurgents from Saudi Arabia, including one described as the leader of an al-Qaida cell.
The men were arrested in Basra province three days after crossing into Iraq across the Saudi border, said Maj. Gen. Adil Daham, chief of the Basra provincial police.
The alleged al-Qaida operative, Ihssan Mijim Khudhir, and three others were found in an abandoned mud hut about 15 miles south of Basra, said Daham.
He gave no other details about their alleged insurgent activity.