Nine Iraqi civilians also died in a series of insurgent attacks in Baghdad and other areas, one day after a bomb killed 30 people in a Shiite farming village northeast of the capital.
The surge in violence occurred as Iraqi political blocs unveiled their lists of candidates for Dec. 15 parliamentary elections, which the United States and its coalition partners hope will help restore enough stability that they can begin sending home their forces next year.
The election commission said Sunday that it has received candidate lists from 21 coalitions and from 207 other political parties or individuals.
Ghalib Abdul-Mahdi, brother of Vice President Adil Abdul-Mahdi, was gunned down along with his driver at 7:45 a.m. while traveling to work at the office of Prime Minister Ibrahim al-Jaafari, two aides to the vice president said.
The aides spoke on condition of anonymity, saying they were not authorized to talk on the record to the media. Ghalib Abdul-Mahdi served as an adviser to the prime minister. One of Iraq's vice presidents is a Shiite and the other is a Sunni. Adil Abdul-Mahdi is a Shiite.
In another part of Baghdad, four gunmen ambushed a convoy carrying acting Trade Minister Qais Dawood Hasan after it left his office in the upscale Mansour neighborhood, police said. Hasan was wounded, two of his guards killed, and six other people injured, five guards and an Iraqi passer-by, said police 1st Lt. Thair Mahmoud and Dr. Mohanad Jawad at Yarmouk Hospital.
On Sunday morning, a roadside bomb destroyed one of several oil tanker trucks driving on a main road in south Baghdad, sending a fire ball up over the area and killing the two men inside, said police Capt. Ibrahim Abdul-Ridha. Four civilian passers-by were wounded.
In Samarra, 60 miles north of Baghdad, a roadside bomb killed a farmer on his tractor and seriously wounded two other civilians, said police Capt. Laith Mohammed.
On Saturday night, U.S. troops backed by helicopters and a jet plane attacked insurgents planning an ambush near the Taji air base about 12 miles north of Baghdad, killing six militants and wounding and capturing five others, the U.S. command said.
The fighting occurred after American troops saw insurgents moving along a canal toward a commonly used ambush site, the U.S. military said in a statement.
The militants fired on Apache attack helicopters who flew to the area for reconnaissance. The helicopters fired back, and the insurgents retreated. When they tried to regroup, an Air Force F-15E jet dropped a 500-pound bomb on them, the military said. Six insurgents were killed and five were wounded and captured, the statement added.
Also Saturday, a bomb hidden in a truck loaded with dates exploded in the center of the Shiite farming village of Huweder, about 45 miles northeast of Baghdad, killing 30 people and wounding 41, said Dr. Ahmed Fouad of nearby Baqouba General Hospital.
The bomb exploded as villagers were heading to the mosque for prayers or outdoors in the cool evening breeze to break the daylong fast they observe during the holy month of Ramadan.
"It felt as if the earth was shaking underneath our feet," said Hussein Mouwaffaq, whose brother Qahtan was killed in the blast. "The street was strewn with dates. Many people were killed and injured."
Police Lt. Ahmed Abdul Wahab, who gave the casualty figure, said the number of deaths could increase because several survivors were critically wounded. The village is in a religiously mixed area plagued by suicide attacks, roadside bombs and armed assaults on police checkpoints.
Shiite civilians are frequent targets of Sunni extremists, including Iraq's most feared terror group, al Qaeda in Iraq, which considers members of the majority religious community to be heretics and collaborators with U.S.-led forces. Iraq's security services are staffed mainly by Shiites and Kurds.
At the hospital in nearby Baqouba, seriously wounded victims lay on stretchers on a blood-smeared floor as doctors and nurses in bloodstained white coats scurried about, trying to cope. Distraught relatives held intravenous bottles beside their loved ones' beds.
On one bed a child lay motionless with a bandage covering his knee, as a man sobbed next to him. A badly burned man writhed in agony on a stretcher as blood ran down his burned skin.
"We ask the terrorists and the so-called mujahedeen: The people who were killed, what did they do?" cried Iraqi army Capt. Ahmed Jassim.
In other developments: