(CNN) -- Dramatic bloodshed Saturday in Iraq left 64 people killed and 190 wounded, two Interior Ministry officials told CNN.
A wave of bombings came amid Eid festivities marking the end of the holy month of Ramadan.
It followed a July that was the bloodiest in five years, when violence between Sunnis and Shiites -- both Muslim sects -- spun out of control.
In a press release Saturday, the State Department said the attacks "bear the hallmarks of suicide and vehicle attacks in Iraq over the past ninety days" and said most of those attacks were committed by al Qaeda in Iraq, which is led by Abu Bakr al-Baghdadi.
"The United States has offered a $10 million reward for information that helps authorities kill or capture Abu Bakr al-Baghdadi," the State Department said, referring to a reward that the U.S. embassy in Baghdad says has existed since 2011.
"This reward is second only to information leading to Ayman al-Zawahiri, the chief of Al Qaeda's network, and symbolizes our ongoing commitment to helping our partners in the region eliminate this threat from their territory."
The Islamic State of Iraq, an umbrella group that includes al Qaeda in Iraq, claimed responsibility for Saturday's attacks on Sunday. The statement, published on an al Qaeda website, said the attacks were in response to recent security force operations.
"The Islamic State mobilized part of its security effort in Baghdad, the southern states and others to deliver a quick message of deterrence on the third day of Eid al-Fitr to the animals of Rawafdh 'Shiite' and their government," the statement said.
Saturday's death toll included reports by Baghdad police that at least 22 people were killed and more than 40 others wounded after eight car bombs exploded in Shiite neighborhoods.
In Tuz Khurmatou, about 180 kilometers, or 112 miles, north of Baghdad, at least eight people were killed and more than 40 others were wounded when a suicide car bomber exploded on a commercial corridor.
Tuz Khurmatou is an ethnically mixed city of Arab, Kurd and Turkmen residents.
In Mosul, at least eight people were killed and 12 others were wounded in two separate explosions in the city. Mosul is a largely Sunni city about 400 kilometers, or 248 miles, north of Baghdad.
In Nasiriya, a car bomb exploded on a busy road, killing four people and wounding 12. Nasiriya is located in the heavily Shiite region of southern Iraq and is about 400 kilometers outside of Baghdad.
In Karbala, about 100 kilometers, or 62 miles, south of Baghdad, a car bomb exploded near a bus station, killing two people and wounding 15 others. Karbala is a Shiite city.
The bloodshed appears to mark a new round of violence to hit Iraq in recent months, much of it stemming from decades-old discord between the nation's Sunnis and Shiites, the two largest branches of Islam.
Sunnis have felt politically marginalized under a Shiite-led government since the ouster of longtime leader Saddam Hussein in a 2003 U.S.-led invasion.
The enmity is further deepened by the fact Saddam's Baathist regime was composed mostly of Sunnis during more than two decades of dictatorship and was violently repressive against Shiites.
July was the deadliest month in Iraq since the peak of sectarian violence in 2006 and 2007. According to figures released by the U.N. Assistance Mission for Iraq, 1,057 Iraqis were killed and another 2,326 were wounded in acts of terrorism and violence last month.