BAGHDAD - Dozens of uniformed gunmen in 17 official vehicles stormed an Oil Ministry compound in Baghdad and abducted a deputy oil minister and three other officials, a ministry spokesman and police said. Outside the capital, a suicide truck bomber struck a strategic bridge, killing at least 10 people, police said.

The attacks came as 16,000 U.S. and Iraqi troops began a new operation north of the Iraqi capital targeting insurgents who have fled a crackdown in the restive city of Baqouba, the military said Tuesday.

Abdel-Jabar al-Wagaa, the senior assistant to Oil Minister Hussain al-Shahristani, was spirited away by more than 50 gunmen wearing security forces uniforms and driving what were believed to be stolen military vehicles, said Assem Jihad, the oil ministry spokesman.

An Interior Minister official, speaking anonymously because he was not authorized to release the information, said a top official in the State Oil Marketing Organization and three directors general in the operation also were kidnapped.

The official said five bodyguards were wounded in the raid on the State Oil Marketing Organization complex in eastern Baghdad.

Five Britons were seized May 29 in a similar raid on Iraq's Finance Ministry, not far from the oil marketing office. They were taken by gunmen wearing police uniforms and have not been found.

Both government organizations are near the lawless Sadr City Shiite enclave. Jihad said the kidnappers were an "armed gang" and took the deputy minister from his home in the compound.

The Thiraa Dijla bridge in Taji, a town near a U.S. air base some 12 miles north of the capital, came under attack around noon, police said, giving the casualty toll.

The bridge, which stretched across a canal on the main highway that links Baghdad with the northern city of Mosul, was bombed three months ago and only one lane had reopened, according to the police officials, who spoke on condition of anonymity because they were not authorized to release the information.

The attacker detonated his payload after going through an Iraqi army checkpoint about 40 yards away from the span, which was devastated, according to the officials.

A number of cars plunged into the canal, which links the Tigris and the Euphrates rivers, and rescue efforts were under way, the officials said.

U.S. and Iraqi troops cordoned off the area to evacuate the wounded, the military said, without providing a casualty toll.

Four more U.S. soldiers were reported killed in separate attacks -- three in an explosion near their vehicle Monday in the northwestern Ninevah province and another who was died of wounds sustained during combat in western Baghdad.

On Tuesday, an American transport helicopter went down during a post-maintenance test flight near Taqaddum air base, in Anbar province, a Sunni insurgent stronghold that has become calmer in recent months as tribal leaders have joined forces against al-Qaida in Iraq.

In an e-mailed statement, 1st Lt. Shawn Mercer, a Marine spokesman, said emergency response crews had sealed off the site and the cause was being investigated. The statement provided no information about how many people were on the helicopter or their status.

The U.S. and Iraq operation north of the capital, dubbed Operation Lightning Hammer, began late Monday with an air assault and was part of a broader U.S. push announced Monday to build on successes in Baghdad and surrounding areas by targeting al-Qaida in Iraq and Iranian-allied Shiite militia fighters nationwide.

Maj. Gen. Benjamin Mixon, commander of U.S. forces in northern Iraq, said the troops were pursuing al-Qaida cells that had been disrupted and forced into hiding by previous operations.

"Our main goal with Lightning Hammer is to eliminate the terrorist organizations ... and show them that they truly have no safe haven -- especially in Diyala," he said in a statement.

Local officials, meanwhile, said four civilians, including a young girl, were killed and five wounded Tuesday during a raid by joint U.S.-Iraqi forces in Baghdad's Shiite district of Sadr City. The U.S. military said four gunmen were killed and eight detained after a fierce gunfight, but it had no reports of civilian deaths.

Associated Press photos showed the body of 6-year-old Zahraa Hussein lying in a wooden coffin, her white nightdress stained with blood. A police official, who spoke on condition of anonymity because he was not authorized to release the information, said the girl and her father had been struck by shrapnel while they slept on the roof of their house seeking relief from the heat.

Spokesman Lt. Col. Christopher Garver said he had no reports of civilians killed in the operation: "We work very hard to avoid any injury to civilians."

The troops raided three buildings in search of a rogue Shiite militia leader suspected of coordinating and conducting attacks against U.S.-led forces and moderate Iraqis, the military said in a statement.

As the armored vehicles were leaving, they were attacked by two roadside bombs and small-arms fire, prompting helicopters to fire warning shots to allow the convoy to escape the attack, it said, adding that U.S.-led ground forces also returned fire.

On the political front, leaders of Iraq's divided factions held a flurry of meetings in preparation for a crisis council planned by Prime Minister Nouri al-Maliki trying to save his crumbling government, which faces allegations of a Shiite bias.

"I think that the circumstances require us to do our best to bring the country out of this difficult situation," Iraq's Sunni Vice President Tariq Hashemi told reporters after holding talks with Kurdish leader Massoud Barzani, who traveled from his autonomous northern region to Baghdad this week to help broker a compromise.

Al-Maliki has struggled over the past days to pull together a meeting of Iraq's main religious and ethnic groups, which had been expected as early as Tuesday.