Like a fiery battering ram, the explosives-filled car blasted the concrete wall surrounding the Palestine Hotel, knocking down a large section about 5:30 p.m. Monday and giving insurgent attackers the opening they needed.

Minutes later, into the breach drove a cement truck refitted as a suicide vehicle. A surveillance camera caught it advancing toward the hotel, used by many foreign journalists and contractors. The way blocked, the driver reversed, apparently looking for another route, before the truck too detonated in an enormous fireball.

The attack was one of the most complex and coordinated that insurgents have launched in Baghdad. Using rockets, small-arms fire and three suicide bombs, they killed at least 16 people and wounded 22, according to government officials, police and witnesses.

The truck blast savaged the exterior of the hotel and some of its rooms, but no one inside was killed, apparently because the truck failed to get close enough.

The attack ended a period of relative calm in Baghdad that began in the days before Iraq's Oct. 15 constitutional referendum. The bombs exploded as restaurants nearby were packed with patrons gathered to break the daily fast of the Muslim holy month of Ramadan.

Police fired shots into the air to enforce a cordon around the area, while ambulances and SUVs from private security companies rushed victims to the neighborhood's Ibn-Nafees Hospital.

Early reports suggested that most of the casualties were Iraqi civilians who were eating in restaurants outside the barrier walls or walking in the streets.

Saleh Mehdi, 40, a laborer who was with a friend at the Chicken Inn restaurant across the street from the complex, said patrons were knocked to the ground. "There was broken glass and shrapnel, and all of the furniture was turned over," he said. "I ran out into the street to escape, and then the second explosion happened. The whole area turned into a battlefield."

Three staff members from Associated Press Television News were wounded, two with head injuries, though none was seriously hurt, according to Rob Celliers, a senior producer. A total of six people inside the compound were wounded, the Associated Press reported.

Iraq's national security adviser, Mowaffak Rubaie, said that five to 10 men had carried out the attack and that journalists were the target.

"This was an attempt to break into the Palestine Hotel and occupy it to take Arab and foreign journalists hostage. Regretfully, this terrorist attack resulted in many civilian casualties," he told the al-Arabiya television network.

Rubaie praised Iraqi police and security companies for helping to thwart the attack.

No American service members were killed or wounded in the assault, which also included rocket fire, according to a U.S. military statement. An American soldier stationed at the site, which also includes the Sheraton Hotel, fired at the oncoming cement truck, helping to disable it, the statement said.

The other vehicle bomb in the attack detonated near an Interior Ministry office behind a mosque on Firdaus Square, where a large statue of former president Saddam Hussein was toppled at the close of the U.S. invasion of Iraq in 2003.

In leaflets distributed by masked gunmen in the western city of Ramadi, an insurgent unit affiliated with the group al Qaeda in Iraq asserted responsibility for the attacks, saying it had struck "the base of blasphemy, crusaders and infidels." The unit, the Lions of Braa Bin Malik, said the attack "killed the manager of the largest security company working in Iraq" as well as "a number of foreigners."

Among the tallest buildings in Baghdad's skyline, the Palestine and Sheraton hotels have been frequent targets of attacks, beginning on April 8, 2003, during the invasion, when an American tank shelled the Palestine, killing two journalists there. The buildings were repeatedly hit by rockets and mortar shells last year but had not been attacked in recent months.

Journalists in the hotel on Monday described a string of huge explosions that devastated the ground level and blew out windows several floors up. "The lobby of the hotel is completely trashed. I found pieces of the cement mixer 150 meters away from where it exploded," said one Western journalist staying at the Palestine, who said his company had asked him not to give his name for safety reasons. "Even by the standard of Baghdad car bombs, this was a large one."

Elsewhere Monday, the military announced that a Marine died Sunday in a firefight in Ramadi.

South of Baghdad, police found the bodies of 18 people who had been shot dead. Twelve of them, discovered in Musayyib, were laborers killed by gunmen driving a black BMW, according to police Capt. Muthanna Ahmed. Six others were found in Iskandariyah, about 30 miles south of the capital, he said.

Al Qaeda in Iraq called Monday for the killing of three prominent Sunni Arab sheiks in the insurgent stronghold of Anbar province, accusing them of working with the U.S. military there. A rift has emerged in recent months between some Iraqi Sunnis, who are believed to make up the bulk of the insurgency, and al Qaeda in Iraq, which is led by Jordanian-born Abu Musab Zarqawi and thought to be dominated by foreign fighters.

Also Monday, the commission tabulating the results of the referendum said that 96 percent of voters in Anbar province had rejected the document, a figure that makes Anbar the second Sunni-majority province to reject the constitution.

To block passage, opponents need to muster two-thirds majorities in three of Iraq's 18 provinces. Nineveh is the lone province with a sizable Sunni population whose results are not yet known. Early reports suggested that the constitution passed there.

Special correspondents Saad Sarhan in Najaf and Bassam Sebti in Baghdad contributed to this report.

A video image taken by a camera on the roof of the Palestine Hotel shows a cement truck, bottom right, moments before it exploded. A car bomb detonated first, clearing a path for the cement truck through a protective wall.