BAGHDAD — A new wave of bombs tore through Baghdad on Monday, officials said, killing at least 55 people. Most of the blasts were car bombs detonated in Shiite neighborhoods, the latest of a series of well-coordinated attacks blamed on hard-line Sunni insurgents determined to rekindle large-scale sectarian conflict.

Multiple coordinated bombing strikes have hit Baghdad repeatedly over the last five months. The Shiite-led government has announced new security measures, conducted counter-insurgency sweeps of areas believed to hold insurgent hideouts, and sponsored political reconciliation talks, but has not significantly slowed the pace of the bombing campaign.

No group immediately claimed responsibility for the bombings, but they bore the hallmarks of al-Qaida's local branch in Iraq, known as the Islamic State of Iraq. Al-Qaida is believed to be trying to build on the Sunni minority's discontent toward what they consider to be second-class treatment by the government and on infighting between political groups.

In addition to helping al-Qaida gain recruits, the political crisis may also be affecting the security forces' ability to get intelligence from Sunni communities.

"Our war with terrorism goes on," Interior Ministry spokesman Saad Maan told The Associated Press. "Part of the problem is the political infighting and regional conflicts ... There are shortcomings and we need to develop our capabilities mainly in the intelligence-gathering efforts."

The deadliest of Monday's bombings was in the eastern Sadr City district, where a parked car bomb tore through a small vegetable market and its parking lot, killing seven people and wounding 16, a police officer said.

Other parked car bombs went off in quick succession in the Shiite neighborhoods of New Baghdad, Habibiya, Sabaa al-Bour, Kazimiyah, Shaab, Ur, Shula as well as the Sunni neighborhoods of Jamiaa and Ghazaliyah. Police officers said 44 people were killed and 139 wounded.

And in the evening, a roadside bomb outside a Sunni mosque within a refinery compound in the south Baghdad district of Dora killed four and wounded 14. Some such attacks on Sunni targets are blamed on hard-line militants targeting rival Sunnis, but there are also indications that Shiite groups have started to retaliate, raising fears of a return to the widespread sectarian killing of 2006-2007.

Medical officials confirmed the casualty figures in Monday's attacks. All officials spoke on condition of anonymity because they were not authorized to talk to the media.

Iraqi security forces sealed off the sites of the attacks as fire fighters struggled to extinguish fires that broke out. The twisted wreckage of cars and remnants of the car bombs littered the pavement.

Iraqi militants often target crowded places such as markets, cafes and mosques, seeking to inflict huge numbers of casualties.

Monday's attacks were the biggest since the Sept. 21 suicide bombings that struck a cluster of funeral tents packed with mourning families in Sadr City, killing at least 104 people.

On Sunday, a series of bombings in different parts of Iraq – including two suicide bombings in the country's relatively peaceful northern Kurdish region – killed 46.

More than 4,500 people have been killed since April. Although overall death tolls are still lower than at the height of the conflict, the cycle of violence is reminiscent of the one that brought Iraq to the brink of civil war.

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Associated Press writer Qassim Abdul-Zahra contributed to this report from Baghdad.

Earlier on HuffPost:

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  • An Iraqi man inspects a burnt-out vehicle at the site of a car bomb explosion in the Hurriyah area of eastern Baghdad, on July 3, 2013 following several attacks the previous day. (AHMAD AL-RUBAYE/AFP/Getty Images)

  • An Iraqi policeman inspects the damage outside a supermarket in central Baghdad's commercial Karrada neighbourhood on June 25, 2013 after a car bomb exploded in the parking area the night before. (ALI AL-SAADI/AFP/Getty Images)

  • A man looks at a destroyed shop following a car bomb in the Shuala area of eastern Baghdad, on July 3, 2013, following several attacks the previous day. (AHMAD AL-RUBAYE/AFP/Getty Images)

  • People and security forces inspect the scene of a car bomb attack in Basra, 340 miles (550 kilometers) southeast of Baghdad, Iraq, Tuesday, July 2, 2013. (AP Photo/ Nabil al-Jurani)

  • Iraqis inspect the aftermath of a car bomb attack at Baghdad's mostly Shiite neighborhood of Husseiniyah, Iraq, Tuesday, June 25, 2013. AP Photo/ Khalid Mohammed)

  • Iraqi men look at the aftermath of a car bomb attack on July 3, 2013 following an explosion the previous day at a convenience store in the northern Baghdad neighbourhood of Shaab. (ALI AL-SAADI/AFP/Getty Images)

  • An Iraqi policeman checks his weapon at a checkpoint in Baghdad on July 1, 2013. (SABAH ARAR/AFP/Getty Images)

  • Iraqis inspect the damage outside shops in Baghdad on June 25, 2013 following an explosion the night before. (SABAH ARAR/AFP/Getty Images)

  • Civilians inspect a crater caused by a car bomb attack in the east Baghdad neighborhood of Kamaliya, Iraq, Wednesday, July 3, 2013. (AP Photo/ Karim kadim)

  • Civilians seen through a broken window of a destroyed car inspect the aftermath of a car bomb attack in the east Baghdad neighborhood of Kamaliya, Iraq, Wednesday, July 3, 2013. (AP Photo/ Karim kadim)