In the worst attack 24 people were slaughtered in a brutal sectarain attack near Baquaba, northeast of Baghdad.
Police say gunmen manning a makeshift checkpoint stopped cars approaching Udhaim, a small town 120 km north of Baghdad, and killed passengers.
Gunman reportedly dragged 24 people, mostly teenager students, from vehicles and shot them dead.
They say the victims included youths aged 15 to 16 who were on their way to the regional town of Baquba for end of term exams, as well as elderly men.
The killings took place in Diyala province, scene of frequent attacks by insurgents waging a campaign of bombings and shootings to topple the US-backed, Shi'ite-led government.
Some tried to flee but were gunned down, a police source said.
Key posts stalled
As violence continued, the country's parliament postponed its session for at least 48 hours due to a lack of agreement over candidates put forward by Mr Maliki for security ministries.
The postponement was to give the prime minister "more opportunity to choose the best and most acceptable candidates for defence and interior," Khaled al-Attiya told reporters.
The postponement came after the different Shiite parties in the dominant United Iraqi Alliance could not agree on the Shiite interior minister.
Candidates disputed
Mr Maliki had originally chosen an independent military figure, but according to Shiite politicians, the Supreme Council for the Islamic Revolution in Iraq (SCIRI), one of the most powerful Shiite parties, wanted one of its own in the post.
Hassan al-Sunaid, a member of the prime minister's Dawa Party, originally told news agency AFP that former Iraqi army general Faruq al-Aariji has been tipped to become the new interior minister.
Mr Aariji is a Shiite currently working as a department head in the ministry.
Instead Mohsen Abdel Hassan, a Shiite general in charge of border security and a member of SCIRI, is now being suggested for the job.
There has been no word about the prime minister's candidate for defence, Abdel Qader al-Obeidi, a Sunni who was the former commander of ground forces in Saddam Hussein's army.
"There is a problem with the two candidates, they are not accepted by all the lists," Haidar al-Abbadi of the Dawa Party told a news conference after the parliament session.
Rice confident
But US Secretary of State Condoleezza Rice was confident that Iraqi politicians would settle the issue in the "next few days."
"The important thing is that they get it right. And when they get it right, and they will get it right, everybody will forget how long it took them," she said on Fox News on Sunday.
Mr Maliki originally named the new government on May 20 without filling the security posts because of continuing disagreement with his broad-based, yet fragile, national unity government.
Filling the security posts is hoped to eventually reverse the steady trend in violence that has engulfed Baghdad and other parts of the country, particularly the southern city of Basra in recent weeks where warring tribes, militias and criminal gangs forced the imposition of martial law.
Eleven people were killed, including two police, in a clash at a Sunni mosque in the early morning hours in Basra.
The latest violence in Basra came only hours after a massive suicide car bomb on Saturday that blew up in a crowded market in Basra killing 28 people and wounding 62. Twelve others were killed in a series of incidents elsewhere.
Gunmen near the village of Ayn Layla northeast of Baghdad stopped vehicles along the road and shot their occupants, killing 20 people including seven minibus drivers and seven students.