In the single deadliest attack, a suicide bomber lured a crowd of Shiite day laborers to his minivan with promises of work before detonating the bomb, which contained up to 500 pounds of explosives, according to the Interior Ministry, reported Reuters.
At least 88 people died and more than 200 were wounded, the Associated Press reported.
Another car bomber blew himself up in northern Baghdad, killing 11 people lined up to refill gas canisters.
Before dawn, gunmen executed 17 men in Taji, a northern suburb of Baghdad.
More than 150 people were killed in all the attacks, which police said appeared to be carefully orchestrated.
On a Web site, al-Qaida claimed it was waging a nationwide suicide bombing campaign to avenge a military offensive on the northern rebel town of Tal Afar, according to Reuters.
Fears of a civil war have grown ahead of the Oct. 15 referendum on a new Iraqi constitution.
Sunnis, who make up about 20 percent of the population, used to dominate Iraqi politics under Saddam Hussein's leadership.
They are concerned that the new constitution will institutionalize their reduced role by granting autonomy to the majority southern Shiites similar to what the Kurds enjoy in the north, and by decentralizing control of oil revenues.
Iraq's parliament sent a "final draft" of the constitution to the United Nations on Wednesday after making minor amendments designed to appease Sunnis, reported Reuters.
U.N. officials said they would not start printing it until they had an assurance from the speaker of parliament that the document was indeed the final version.
Meanwhile, Iraq's interim President Jalal Talabani met with President Bush in Washington this week ahead of a U.N. summit in New York. Talabani said he would not set a timetable for U.S. troops to leave Iraq and that he hoped Iraqi security forces would be ready to start taking over by the end of 2006.