The U.S. military said 14 American troops have died in multiple attacks, including five killed Thursday in a single roadside bombing in Baghdad.

Elsewhere, a suicide truck bomber struck the Sulaiman Bek city hall in a predominantly Sunni area of northern Iraq, killing at least 16 people and wounding 67, an Iraqi commander said.

Thousands of protesters also rallied in the Shiite holy city of Najaf, 100 miles south of Baghdad, waving Iraqi flags and the black and green Shiite banners with slogans such as "Death to Al Qaeda" in a show of unity following the bombing that brought down the twin minarets of a revered mosque in Samarra.

The latest U.S. deaths raised to at least 3,545 the number of American troops who have died since the war began in 2003, according to an Associated Press count.

The deadliest attack was a roadside bomb that struck a convoy in northeastern Baghdad on Thursday, killing five U.S. soldiers, three Iraqi civilians and one Iraqi interpreter, the military said.

A rocket-propelled grenade struck a vehicle in northern Baghdad about 12:30 p.m. Thursday, killing one soldier and wounding three others, another statement said.

On Wednesday, another powerful roadside bomb killed four U.S. soldiers and wounded another in western Baghdad, while two Marines died in fighting in Anbar province, to the west of the capital.

Southwest of Baghdad, two soldiers were killed and four were wounded Tuesday when explosions struck near their vehicle, the military said, correcting an earlier statement that gave the date of the attack as Wednesday.

Counting a previously announced U.S. fatality that occurred Tuesday, the latest military statements meant that 15 troops were killed over a three-day period.

The explosion in Sulaiman Bek occurred about 10:30 a.m., and killed 16 people, Maj. Gen. Anwar Hama Amin said. The commander of the Iraqi army's 2nd Brigade blamed the blast on Al Qaeda, saying it was the latest in a series of strikes by the terror network against government officials, whom they accuse of collaborating with the U.S. and the Iraqi government.

Sulaiman Bek is about 100 miles north of the capital and just outside the border with Diyala province, where thousands of U.S. troops are engaged in an offensive against Al Qaeda in Iraq.

Amin said the target apparently was the mayor, who has lost five relatives in previous assassination attempts. The blast heavily damaged the city hall, along with several nearby houses and stores.

Thamir Mohammed, a 28-year-old newlywed, said he was on his way to city hall to do some paperwork to get a new ration card when the blast occurred, knocking him off his feet and wounding him in the head and legs.

"I was walking in the street heading to the city hall when a truck drove up and parked outside. The driver got out and was just outside the truck when the explosion took place," Mohammed said from his hospital bed in nearby Tuz Khormato.

It was the latest in a series of attacks as Al Qaeda fights back as the U.S. intensifies operations against the terror network in Baghdad and elsewhere around the capital.

A U.S. airstrike aimed at a booby-trapped house in one of the centers of those offensives, the Diyala provincial capital of Baqouba, missed its target and "accidentally hit" another structure, wounding 11 civilians on Wednesday, the military said, adding the incident was under investigation.

U.S. troops had cleared the area to destroy a house containing explosives believed placed by Al Qaeda, but "the bomb missed its intended target and struck another structure," the military said. "Reports indicate that 11 civilians were injured."

The initial target was later destroyed by a Hellfire missile, producing a large secondary explosion, according to the statement.

A spokesman for the 1920s Revolution Brigades, a nationalist Sunni insurgent group that has begun cooperating with U.S. and Iraqi forces in the fight against al-Qaida in Diyala, said an airstrike mistakenly struck a building being used as a headquarters by the group. The spokesman, who declined to be identified due to security concerns, said two members were killed and four were wounded.

Maj. Gen. Abdul Karim al-Rubaie of the Iraqi army said the offensive that began Monday in Diyala was going well and operations were focused on the areas of Jurf al-Milih and the northern part of the Baqouba market, which has been the site of several recent execution-style killings by Al Qaeda.

Hospital officials said ambulances were bringing dozens of bodies of militants who have been killed from the western half of the city, which was under a strict curfew.

The latest military report on the Diyala offensive said U.S.-led forces had killed 41 insurgents, discovered five weapons caches and destroyed 25 bombs and five booby-trapped houses.

With all of the nearly 30,000 additional troops ordered to Iraq by President Bush now in place, the military said the massive operations on Baghdad's flanks were "a powerful crackdown to defeat extremists" and named the combined offensives "Operation Phantom Thunder."

A bombing that destroyed the golden dome of the Askariya mosque in Samarra on Feb. 26, 2006, set in motion an unrelenting cycle of retaliatory sectarian bloodletting, but the son of a top Shiite politician blamed the violence on Sunni extremists and Saddam Hussein loyalists, and urged the Najaf demonstrators to maintain peace.

Ammar al-Hakim — whose father Abdul-Aziz al-Hakim, the leader of the Supreme Islamic Council of Iraq, is in Iran for cancer treatment — also criticized a U.S.-Iraqi security plan in Baghdad and surrounding areas, which is now in its fifth month.

"The security situation in Baghdad, Diyala and other areas shows that the security plan needs revision and development in order to achieve greater results," he said. "We demand that the government shoulder responsibility in this revision and put forward the necessary plans to impose security. Security and services are vital and they should be the top priority of the Iraqi government."

Violence persisted in Baghdad, with a series of mortars or rockets slammed into the U.S.-controlled Green Zone, which houses the U.S. and British embassies and major Iraqi government headquarters — raising fresh concerns about the thousands of Americans who live and work in the heavily fortified area in central Baghdad.

A huge plume of black smoke rose from the sprawling complex on the west bank of the Tigris River and helicopters buzzed overhead after about nine blasts occurred in quick succession around 10 a.m.

At least one mortar round struck a parking lot used by Prime Minister Nouri al-Maliki and his security detail, an official from his office said, speaking on condition of anonymity because he wasn't authorized to release the information.

The U.S. Embassy confirmed rounds of indirect fire, the military term for rockets or mortars, but said it did not have information about casualties.

Elsewhere, sports officials gathered for a funeral for an Iraqi bodybuilding champion, Mahir Mohammed Ali, who was killed in the bombing of a Shiite mosque Tuesday in central Baghdad.

At least 21 people were killed or found dead in attacks nationwide, including the director of a branch office of radical Shiite cleric Muqtada al-Sadr who was shot to death near the southern city of Hillah.