BAGHDAD -- Insurgents struck Baghdad with at least a dozen attacks that targeted Shi'ite Muslim civilians, Iraqi security forces, and American troops, killing more than 160 people yesterday in the deadliest day of violence in the capital since the US invasion.
US military officials said the daylong waves of suicide bombings, rocket attacks, and shootings across the city bore the hallmarks of Al Qaeda in Iraq, the radical Sunni Muslim insurgent organization led by Abu Musab al-Zarqawi.
The group did not immediately assert direct responsibility for the attacks, but an Internet statement issued in its name welcomed the start of ''the revenge battles throughout the land of Mesopotamia."
The statement linked the attacks to a US and Iraqi offensive underway against insurgents in the northern city of Tal Afar, and a subsequent audio recording attributed to Zarqawi that was posted on the Internet accused the Shi'ite-led Iraqi government of having declared war on the Sunnis of Tal Afar. As a result, Al Qaeda in Iraq ''has decided to launch a comprehensive war on the Shi'ites all over Iraq, wherever and whenever they are found. This is revenge. . . . Take care, because we are not going to have mercy on you," the recording said, according to a translation by the SITE Institute, a group based in Washington that monitors radical websites.
The spasm of violence continued this morning. A suicide bomber drove his car into a convoy of police vehicles in Baghdad's southern Dora district, killing 16 officers and five civilians. Lieutenant Thair Mahmoud of the Rapid Response Unit said 21 people were injured in the blast, which destroyed three police vehicles.
The attacks appeared calculated to undermine public faith in the ability of the fledgling government to protect its people, by showing that insurgents can strike in Baghdad despite the US and Iraqi military efforts to stop them. Some of yesterday's attacks were carried out in ways that maximized death tolls.
In northwest Baghdad, a driver in the heavily Shi'ite neighborhood of Kazimiyah pulled up alongside a gathering point for day laborers and offered jobs, witnesses said. He waited until a crowd of workers had clustered around his four-door car, then detonated explosives packed inside, said 20-year-old Salim Hussein, who witnessed the attack.
The blast killed at least 112 people and wounded hundreds of others.
As burned, blackened victims filled the district hospital, a Shi'ite cleric patrolled the scene of the bombing in an ambulance, calling over the vehicle's loudspeaker for donations of blood. Men ran fingers down pages and pages of names of bombing victims posted outside the hospital, looking for loved ones.
''Why haven't they killed Saddam?" wailed a Shi'ite woman in black abaya as she walked away from the hospital.
Within an hour of the first attack, another driver smashed his car into two other vehicles at an intersection, then blew up his car in a fireball when a crowd gathered, police said. At least 15 people died, police Lieutenant Mustafa Majid said. ''I saw people's bodies flying in the air and thrown for yards," minibus-taxi driver Amer Salman said.
More attacks were mounted throughout the day, signaled by rattling booms, black smoke, and US military helicopters shuttling across the sky. Traffic on main roads shut down as police closed key routes. Rumors spread that more car bombers were roaming the city and that men wearing suicide belts were infiltrating hospitals.
The other attacks included two car bombings that killed a total of 26 people, one that targeted an Iraqi Army convoy and killed three soldiers, and two that hit US military convoys, US and Iraqi officials said. A US military spokesman, Lieutenant Colonel Steve Boylan, said he knew of three American troops wounded in the day's attacks and that none had been reported killed.
Separately, attackers opened fire on a car carrying Iraqi police officers, killing one, and then detonated a car bomb when other officers responded, killing four more people, police said. A separate rocket attack killed two civilians.
In Taji, a town just north of Baghdad, men wearing Iraqi security-force uniforms dragged 17 men out of their homes, then handcuffed, blindfolded, and shot them, news agencies reported.
A US military convoy came under intense attack in the late afternoon, first with a roadside bomb, and then with a car bomb, police said. A reporter watched as US forces traded gunfire with hidden assailants at the scene.
One of the final bombings of the day hit outside the Green Zone, the barricaded base of US officials and the Iraqi government. There was no immediate word on casualties.
The death toll made yesterday the deadliest day of insurgent violence in Baghdad since the United States and its allies invaded Iraq in March 2003. The deadliest day of insurgent violence nationwide was March 2, 2004, when at least 181 people were killed in mortar and bomb attacks on Shi'ite shrines in Karbala and Baghdad.
Material from Reuters was used in this report.