Unknown gunmen opened fire on the convoy injuring three as it was returning from the city of Karbala, Intifadh Qanbar, an official with Chalabi's Iraqi National Congress Party, said. Police said one bodyguard was killed.
Chalabi himself however was not aboard the vehicle.
"The attackers opened fire from both sides of the motorway," a guard said from Baghdad's Yarmuk hospital where he was being treated.
"We responded and exchanged fire for half an hour before the Iraqi army arrived."
Three of the attackers were killed and another wounded and captured, a Defence Ministry source said.
The ambush occurred in a town south of Baghdad, Latifiya. Two cars were destroyed during the attack.
An armed group in Iraq calling itself the Imam Hussein Brigades announced, in a statement posted on the internet, it carried out the attack. The claim could not be verified.
Two of Chalabi's bodyguards were killed in an attack on his convoy in the same area last September.
Former Pentagon favourite Chalabi, a secular Shia Muslim, achieved a remarkable political recovery when he was made one of premier Ibrahim al-Jaafari's deputies in his government announced in May.
Chalabi, a former ally of the United States also lobbied strongly in Washington for the invasion of Iraq and plays a key role in setting oil policy in the country.
Earlier on Sunday a car bomb has exploded near an Iraqi police checkpoint south of Baghdad, killing seven people, police said, while the US military announced that five soldiers had been killed in two bomb attacks a day earlier.
The car bomb attack occurred about 50km south of Baghdad near the town of Haswa, the police department in nearby Hilla said.
The explosives-packed vehicle had been left by the side of the road, near the checkpoint, and was detonated remotely.
All of those killed were civilians, the police said. Twelve people were wounded, three of them police officers.
The area south of Baghdad, in and around Hilla, has been dubbed "the triangle of death" by US forces because of the frequency of attacks.
Iraqi forces have set up checkpoints in the area to stem attacks.
US marines used tanks and aircraft to battle fighters in western Iraq on Sunday after the Americans came under attack from a village schoolhouse, the US military said. Eleven fighters were killed, the military said.
The battle started when marines from Regimental Combat Team-2 were attacked with mortar fire from fighters firing from a schoolhouse in a village near Haditha, 220km northwest of Baghdad.
US Abrams tanks and jet aircraft
attacked the school
The building was rigged with explosives and fortified with at least three .30 caliber machine guns in the windows, a military statement said.
US Abrams tanks and jet aircraft attacked the school, setting off secondary explosions from the munitions stored inside, the statement added.
"Coalition forces on the scene described the secondary explosions as being larger detonations than the bombs that were dropped," the statement added. "There were no civilian casualties. The school was not in session, and 11 insurgents were confirmed killed."
US soldiers killed
On Saturday, five US soldiers were killed and two wounded in two bomb attacks on their patrols in the Iraqi capital, the US military said on Sunday.
One soldier was killed and two wounded when their military vehicle was blown up in the capital's southern district of Dora.
Another four soldiers were killed in a second bomb attack in southwest Baghdad, Sergeant David Abrams said.
The deaths brought the total number of US military personnel who have died in Iraq since the March 2003 invasion to 1793 according to an AFP tally based on Pentagon figures.