A car bomb in Baghdad's northeastern and mostly Shiite neighborhood of Husseiniyah killed another seven people and wounded 31.
Iraqi officials are tightening security ahead of the Eid al-Fitr holiday that marks the end of the Muslim holy month of Ramadan this weekend. Authorities are seeking to thwart a possible upsurge in violence as crowds gather in public places such as parks, shrines and mosques to mark the occasion.
"Our security forces have received intelligence that terrorist groups are planning and preparing for attacks during and after Eid," said Abdul-Karim Tharib, head of the Baghdad provincial council security committee. "We ... have taken all necessary measures to foil any terrorist activities during Eid."
An interior ministry official said security measures for the holiday will include an increased number of checkpoints and road closures near government offices, parks and shrines. He spoke on condition of anonymity because he was not authorized to release details of the security preparations.
Thursday's carnage began when militants planted four bombs around the house of a military officer near the northern city of Kirkuk, according to the city's police commander, Brig. Gen. Sarhad Qadir. The officer escaped unharmed, but his brother was killed and six other family members were wounded.
Hours later, a bomb in a parked car exploded near a string of restaurants, killing one and wounding 15, Qadir said. The blast seriously damaged the eateries' storefronts, scattering shattered glass and debris across the sidewalk.
Another parked car bomb blast targeting a police patrol followed, wounding two policemen and two bystanders. A couple hours later, two car bombs exploded simultaneously in a Kirkuk parking lot near a complex of government offices in the city's north, injuring four people.
Kirkuk, 180 miles north of Baghdad, is home to a combustible mix of Kurds, Sunni Arabs and Turkomen. They all claim rights to the city and the oil-rich lands around it. Daqouq, the site of the midday blast, is about 19 miles south of the city.
Just north of Baghdad, in the Sunni city of Taji, yet another parked car bomb went off next to a passing police patrol, killing two civilians who were standing nearby. Seven people, including police and civilian bystanders, were wounded, police said.
About 40 miles west of Baghdad, militants in speeding cars opened fire on a police patrol in the former insurgent stronghold of Fallujah, killing four policemen and injuring three others, a police officer said.
In Baaj, a remote northwestern town near the Syrian border, gunmen shot dead two civilians who were walking in a market, police said.
Health officials in nearby hospitals confirmed the casualty figures. Most officials spoke on condition of anonymity about the day's violence as they were not authorized to release information to journalists.
There was no immediate claim of responsibility for Thursday's attacks, but they bore the hallmarks of al-Qaida's Iraqi branch. The group has said it aims to reclaim areas from which it was routed by U.S. forces and their local allies.
Thursday's violence comes a day after militant strikes in northern Iraq left 13 people dead.
The al-Qaida offshoot, known as the Islamic State of Iraq, has for years had a hot-and-cold relationship with the global terror network's leadership.
Both shared the goal of targeting the U.S. military in Iraq and, to an extent, undermining the Shiite government that replaced Saddam Hussein's regime. But al-Qaida leaders Osama bin Laden and Ayman al-Zawahri distanced themselves from the Iraqi militants in 2007 for also killing Iraqi civilians instead of focusing on Western targets.
Generally, al-Qaida in Iraq does not launch attacks or otherwise operate beyond Iraq's borders. But in early 2012, al-Zawahri urged Iraqi insurgents to support the Sunni-based uprising in neighboring Syria against President Bashar Assad, an Alawite. The sect is an offshoot of Shiite Islam.
Thursday's attacks were Iraq's deadliest since July 23, when a string of coordinated bombings and shootings left more than 100 dead.