Troops from the Army's Stryker Brigade Combat Team detained nine people and seized weapons in the overnight sweeps in Mosul, the military said Thursday.
U.S. forces have intensified nighttime operations in Iraq's third largest city in a race to make it safe enough for voters to cast ballots in the country's Jan. 30 parliamentary and regional elections. In the past two weeks alone, U.S. and Iraqi forces have rounded up 200 suspected insurgents there, the U.S. military said.
A surge in car bombings and street clashes in the city have followed November's devastating U.S. offensive in the former insurgent hub of Fallujah, and U.S. commanders believe many rebel fighters who fled that siege have set up new operations in Mosul and other cities.
In other developments:
In northern Iraq, a Brazilian citizen was reported missing after insurgents fired on his car in a highway ambush Wednesday that killed a British contract security worker and an Iraqi guard, Iraqi police Lt. Shaalan Allawi said.
The security team was employed to protect a power station in the central city of Beiji, their company said.
Earlier, Iraqi police had said the missing foreigner was a Japanese engineer, but later said he was from Brazil.
The security personnel worked for the British-based Janusian Security Risk Management, Ltd.
"We are proud of their professionalism and dedication and of the role they played in trying to help in the reconstruction of that country," said David Claridge, managing director of the firm. "We are investigating the matter and are working with the local authorities in their efforts to locate the missing civilian."
News video footage of the aftermath of the attack showed two cars riddled with bullets and the ground soaked with blood.
Baghdad appeared mostly calm Thursday, following a wave of deadly car bombings that sent thunderous booms rattling windows throughout city.
The five blasts, including a truck bomb outside the Australian Embassy, seemed well coordinated, with four of them rocking different parts of the city within a span of 90 minutes Wednesday morning.
On Thursday morning, motorists reported that major highways leading into the capital from the west and south were sealed by Iraqi forces.
Alaa Mahmoud, an Iraqi National Guard captain at the scene of one roadblock, said he was under orders to prevent all vehicle traffic from entering the city. Government officials could not be reached for comment because offices were closed at the start of a four-day Muslim holiday.
During Muslim prayers Thursday to mark the feast of Eid al-Adha — which coincides with the yearly pilgrimage to Mecca in Saudi Arabia — a cleric at a Baghdad mosque offered a sour reflection on the effect violence has had on life in the capital.
"Baghdad is the city of science, city of kings, city of believers. It has now become the city of explosions and hideout of criminals," Mohammed al-Sumeidi said in his sermon.
Sunni Muslim insurgents have threatened to disrupt this month's elections and Wednesday's rebel offensive on the capital demonstrated the grave threat facing Iraqis at this watershed in their history.
Nevertheless, the car bomb attacks had little effect on preparations for the Jan. 30 balloting, in which Iraqis will choose a 275-member National Assembly and regional legislatures. At Baghdad airport, Iraqi authorities Wednesday received the largest shipment of ballot boxes and other elections equipment to date.
Interim Prime Minister Ayad Allawi, meanwhile, said he was discussing with American officials how to accelerate the training and arming of Iraqi security forces to help speed the withdrawal of foreign troops from the country.
The presence of foreign troops is an issue that threatens to keep some voters away from this month's elections. Some Sunni clerics have called for a boycott of the vote, in part because they say it should not take place while the country is occupied.
Although the country's majority Shiite Muslims and the Kurds are expected to vote in large numbers, officials fear a low turnout among Sunni Arabs may cast doubt on the legitimacy of the new government and sharpen communal tensions among the country's 26 million people.