In its post on jihadist forums, the Islamic State of Iraq called the attacks a "first stage" that will be followed by "revenge," Voice of America reported.
The attacks -- 17 car bombs, seven roadside bombs and two shootings -- occurred mostly in Shiite neighborhoods of Baghdad, but also hit Sunni communities in other towns north and south of the Iraqi capital, CNN reported. At least 200 people were wounded.
Early Wednesday another car bomb detonated in Baghdad, killing two people and injuring five others, officials said.
Tuesday's attacks happened on the eve of the 10th anniversary of the U.S.-led invasion of Iraq.
Ramzy Mardini, an expert on Iraq, told CNN the attacks likely were "pre-scheduled for the anniversary."
Mardini said he thinks such attacks indicate a revival of "capability and confidence" of al-Qaida in Iraq that's buttressed by a Syrian uprising "spearheaded by Sunni militancy."
U.S. President Obama issued a statement Tuesday on the anniversary of the invasion, honoring the 1.5 million Americans who served "in one of our nation's longest wars." U.S. troops withdrew from Iraq in December 2011.
Obama said the 4,475 U.S. military personnel who died "made the ultimate sacrifice to give the Iraqi people an opportunity to forge their own future after many years of hardship."
Elsewhere in Washington, recognition of the anniversary was muted, The New York Times reported.
Defense Secretary Chuck Hagel, who broke with his party when he was a Republican senator, issued a statement praising the troops and urging Americans to "remember these quiet heroes this week."
Former President George W. Bush and former Vice President Dick Cheney offered no public comment, the Time said. Former Defense Secretary Donald H. Rumsfeld posted on his Twitter page: "10 yrs ago began the long, difficult work of liberating 25 mil Iraqis. All who played a role in history deserve our respect & appreciation."
"This is a little like the crazy uncle in the attic that nobody wants to talk about," said John Nagl, a retired Army lieutenant colonel who served in Iraq. "But we need to because we put him there.
"It would be a shame if we did not pause and think hard about this as a nation," said Nagl, a war critic and fellow at the Center for a New American Security in Washington. "We paid an enormous price as a nation. The Iraqis have paid a huge price. The region is destabilized."
A CBS News Poll released Tuesday indicated 54 percent of Americans said the United States should have stayed out of Iraq, while 38 percent said it did the right thing. Fifty percent said the United States did not succeed in achieving its objectives, while 41 percent said it did.