Baghdad (CNN) -- An al-Qaeda affiliate claimed responsibility Wednesday for a chain of 24 bombings and two gun attacks in Iraq a day earlier, as the death toll rose to 61.
A statement attributed to the Islamic State of Iraq appeared on extremist websites, calling Tuesday's carnage "retaliation" against Shiite members in government.
Though Iraq has grown safer in the last six years, sectarian violence and instability still grip the country 10 years after the start of the U.S.-led war.
The attacks -- 17 car bombs, seven roadside bombs, and two shootings -- ripped mostly through Shiite neighborhoods of Baghdad, but also struck Sunni communities in other towns. At least 200 people were wounded.
Early Wednesday another car bomb detonated on a busy square, killing two people and injuring five more.
The level of carnage has dropped considerably since the height of the sectarian violence in 2006 and 2007 that nearly tore Iraq apart. But the continuing violence serves as a near daily reminder of the threat to the fragile political and economic gains in a post-Saddam Hussein Iraq.
It's the second time in less than a week that the Iraqi capital has endured major simultaneous attacks.
Ten years on, the war left more than 134,000 Iraqis and more than 4,800 U.S. and other coalition service members dead. The war cost hundreds of billions of dollars.
"It remains entrenched and pervasive, with a clear beginning but no foreseeable end, and very much a part of the present in Iraq," said Iraq Body Count, a UK-based group that tracks war deaths.
"In major regions of the country armed violence continues to exact a remorseless toll on human life, young and old, male and female, across society."
In Tuesday's violence, car bombs rocked Baghdad neighborhoods long engulfed in conflict, like Shulaa and Kadhimiya. They struck Mustansiriya University in eastern Baghdad and the fortified International Zone, also known as the Green Zone, where the city's international presence is concentrated. They hit cities north and south of the capital as well. Authorities defused four car bombs in the southern city of Basra.
Attackers also struck in the provinces of Anbar, Kirkuk, Babel, Nineva, and Diyala.
They set off roadside bombs in Baghdad's teeming Shiite slum of Sadr City.
Iraq is still on pins and needles
Change can be seen in the once war-torn nation. A robust form of democracy has taken hold. Sunnis, Shiites, Kurds and others often work together. There is more political, economic and social stability. Coalition forces that ousted Hussein's government have departed.
However, recent attacks in Shiite areas have spread fear among Iraqis that sectarian warfare between Sunnis and Shiites may ravage the country again.
Sunnis had more political clout during Hussein's reign. The Shiites and the Kurds, the other two main groups, were second-class citizens. Since Hussein was toppled, the tables have turned. Shiites -- the largest religious group in the country -- predominate in government. The Kurdish semiautonomous region in the north, and the Kurds themselves, have more clout.
Today, Sunnis feel they've been politically marginalized. They demand that the Shiite-led government stop what they call negative treatment of Iraq's Sunni community.
Expert: Syria and Iraq connected
Ramzy Mardini, an expert on Iraq, said the attacks were probably "prescheduled for the anniversary." He also said the latest violence reflects the Sunni-Shiite sectarian tensions raging next door in Syria.
He believes such attacks illustrate the revival of the "capability and confidence" of al Qaeda in Iraq, buoyed by a Syrian uprising "spearheaded by Sunni militancy."
It stands to reason that the attackers are targeting the government of Iraqi Prime Minister Nuri al-Maliki. The Shiite-dominated government is helping neighboring Iran, the largest Shiite nation in the world and a supporter of the Alawite-dominated Syrian government.
"Al Qaeda in Iraq is becoming less exclusive to Iraq. They are trying to channel energy and piggyback off the Syrian revolution by aiming to merge Iraq and Syria into one theater of sectarian war," said Mardini, adjunct fellow at the Iraq Institute for Strategic Studies in Beirut, Lebanon.
"Given that Maliki is helping Iran prop up the Syrian regime, AQI is advertising their cause and looking to attract the support and resources of militant groups in Syria."
Obama administration marks the milestone
U.S. President Barack Obama and Secretary of State Chuck Hagel marked the 10th anniversary of the war's beginning with statements praising the service members who fought in Iraq. Obama honored the more than 1.5 million service members and civilians who served there and the memory of the nearly 4,500 Americans who died there.
"The last of our troops left Iraq with their heads held high in 2011, and the United States continues to work with our Iraqi partners to advance our shared interest in security and peace."
Obama said a strong Post-9/11 GI Bill would help veterans pursue jobs and education.
"We must ensure that the more than 30,000 Americans wounded in Iraq receive the care and benefits they deserve and that we continue to improve treatment for traumatic brain injury and post-traumatic stress disorder."
Hagel and Obama also praised the sacrifices of service members' families.
CNN's Mohammed Tawfeeq reported from Baghdad. CNN's Joe Sterling reported from Atlanta.