Wednesday's worst attack took place near Baqouba, 35 miles northeast of Baghdad, and began when gunmen stopped a bus taking employees to work at the state-run Diyala Electronics Co., which makes products such as televisions.

After ordering women off the bus, the insurgents shot and killed the men inside, said Adnan Hamad, a company spokesman. Another company bus then stopped and rushed to rescue the wounded. When the door of the bus opened, a bomb exploded inside, he said.

The final death toll was 11 killed and six wounded, said Hamad.

In Baghdad, gunmen also fatally shot Mohammed Musaab Talal al-Amari, a Shiite who directs the Defense Ministry's public relations office, said police Capt. Jamil Hussein. Al-Amari was on his way to work when his car was stopped by another vehicle in the residential neighborhood of Bayaa, Hussein said. Three men then got out of another car and opened fire, killing him and wounding an Iraqi pedestrian, he said.

In two other shootings in Baghdad, suspected insurgents killed a Shiite taxi driver and a Shiite who once belonged to Iraq's disbanded Baath party, police said. A similar attack killed a civilian driver about 80 miles south of the capital.

Gunmen also killed four off-duty policemen in an ambush Tuesday in Ramadi, apparently as they were leaving work. Ramadi is located in the western Anbar province, where many Sunni-led insurgent groups are based.

The suicide attack in Tal Afar, 260 miles northwest of Baghdad, occurred Tuesday evening as shoppers were scurrying to finish their purchases before closing, police said. The attacker had attracted a crowd of people to his pickup truck by hawking flour at half-price, police said.

Lt. Col. Ali Rasheed of the Interior Ministry said the main target of the bombing may have been a police station within the market area.

The director of the city hospital, Saleh Qado, said 20 people were killed and 70 wounded, but the U.S. command said Wednesday that 134 Iraqis were wounded, at least 24 of them critically.

As casualties mounted at the local hospital, the overflow of wounded were taken to nearby coalition medical facilities, the command said. Some of the critically wounded also were flown on coalition aircraft to hospitals in Mosul and Tikrit.

At least 500 Iraqis have been killed by vehicle bombs in 2006, out of a total of at least 3,525 Iraqis killed in war-related violence this year. These numbers include civilians, government officials, and police and security officials, and are considered only a minimum based on Associated Press reporting.

In March, President Bush praised American efforts to stabilize Tal Afar, saying he had "confidence in our strategy" and that success in the city "gives reason for hope for a free Iraq."

U.S. and Iraqi forces launched an operation in September to clear the city of insurgents ¡ª the second such attempt in a year. However, by the end of that month a woman suicide bomber slipped into a crowd of recruits, killing at least six people and wounding 30. Since then, the city has been hit by repeated suicide attacks.

Tal Afar's population is a volatile mix of Turkomen, Kurds and Arabs, which complicates efforts to control the city. Trouble started in 2003 when Kurdish fighters took over the city, angering the majority Turkomen population.

Insurgents are also believed to have used Tal Afar as a hub for smuggling weapons and fighters from Syria, about 90 miles to the west.