The bomb, according to Police Lt. Bilal Ali, was in a car parked near a gas station in the Bab Shargi section of the Iraqi capital.
It happened at about 9:45 a.m.
Also Wednesday, U.S. officials said that a soldier and three more Marines have died – as a result of combat wounds suffered in the Iraqi province of Anbar – which has been a stronghold for insurgents.
Tuesday, as shock spread through Iraq over a mass kidnapping of scientists by abductors said to have been wearing government uniforms, a series of car bombs exploded around Iraq, killing and wounding scores of people.
Suspected Shiite militiamen dressed as Interior Ministry commandos stormed a Higher Education Ministry office Tuesday and kidnapped dozens of people after clearing the area under the guise of providing security for what they claimed would be a visit by the U.S. ambassador.
CBS News correspondent Elizabeth Palmer reports that about 80 men in Iraqi police uniforms surrounded an Iraqi Ministry of Higher Education building in broad daylight and then moved inside, according to witnesses.
There are varying estimates of the number of people kidnapped, but it appeared that at least 50 were seized — one of the largest mass abductions in Iraq.
Authorities said as many as 20 were later released, but said a broadcast report that most hostages were freed appeared to be false.
Witnesses and authorities said the gunmen raced through all four stories of the building, forced men and women into separate rooms, handcuffed the men and loaded them aboard about 20 pickup trucks.
But by the time help arrived, the kidnappers had vanished with their hostages, leaving signs of a struggle, but few clues. As police cordoned off the building, news of the raid spread to relatives — who know very well what happens to most abduction victims in Iraq, Palmer reports.
Shortly afterward, authorities arrested six senior police officers in connection with the abductions — the police chief and five top subordinates in the Karradah district, the central Baghdad region where the kidnappers struck, Interior Ministry spokesman Maj. Gen. Jalil Khalaf said.
In other developments:
The assault came on a day that saw at least 117 people die in the mounting disorder and violence gripping the country.
The abductions in broad daylight raised further questions about Prime Minister Nouri al-Maliki's commitment to wiping out the heavily armed Shiite militias of his prime political backers: the Supreme Council for the Islamic Revolution in Iraq, or SCIRI, and the Sadrist Movement of radical, anti-American Shiite cleric Muqtada al-Sadr.