Car bombs and other explosions ripped through Iraq's capital and a major northern city on Tuesday, killing nine people and showing again the ease with which insurgents manage to slip past security.

The explosions in Baghdad and Mosul came exactly a week after suicide bombers killed 127 people and wounded more than 500 in a series of five bombings in the Iraqi capital — three of which appeared to target government buildings.

The blasts raise fresh questions about the government's ability to protect itself and its citizens as U.S. forces prepare to leave Iraq.

"There were two military checkpoints using detectors at the beginning of the street, how can such car bombs manage to enter and explode?" said a Baghdad woman who identified herself as Um Ali, her cheeks smeared with blood as she screamed at reporters, echoing the frustrations voiced by many Iraqis.

In Baghdad, three car bombs detonated within minutes of each other in different areas near the heavily guarded Green Zone, which houses the U.S. Embassy, the Iraqi parliament and other government buildings.

One of the bombs went off near the Foreign Ministry, which was targeted in an August bombing; two others exploded near the Immigration Ministry and the Iranian Embassy.

Five people were killed and at least 16 wounded, according to Iraqi officials who spoke on condition of anonymity because they were not authorized to talk to the media. Authorities quickly arrested owners of three parking lots where the bombs exploded, charging them with failing to carefully search the cars and check vehicle registration papers.

Hours later and hundreds of miles away, in the northern Iraqi city of Mosul, two more car bombs an a roadside mine killed four people. A doctor at the Mosul general hospital said as many as 40 were wounded in the separate blasts that appeared to target a high-traffic neighborhood and a church.

Mosul is Al Qaeda's last urban stronghold in Iraq.

Baghdad is still reeling from last week's suicide bombings, which mirrored the Aug. 19 and Oct. 25 attacks that targeted government ministries and buildings and left more than 250 people dead.

Together, the three massive bombings have sparked outrage among Iraqi lawmakers who want Prime Minister Nouri al-Maliki and his top aides be held accountable for what they describe as gaping, and continuing, security breaches.

Talking to reporters outside the Green Zone, Parliament Speaker Ayad al-Samarraie denounced Tuesday's explosions in Baghdad and Mosul as "heinous crimes." He lashed out at Iraq's intelligence services, saying that their work "is less than what is needed and it has not risen to the challenges Iraq is facing."

"There must be a firm stance, immediate measures and a review to all security plans," al-Samarraie said.

Thick clouds of black smoke could be seen lingering over the area. Firefighters and neighborhood residents worked to put out fires, while Iraqi security forces fired their guns into the air to disperse growing crowds.

A TV cameraman was injured in one of the blasts as he waited among a group of journalists headed on a government-sponsored trip to a camp housing Iranian exiles near the border with Iran. It was not immediately clear who the cameraman worked for, or the extent of his injuries, said an Associated Press reporter at the scene.

About an hour after the 7:30 a.m. explosions in Baghdad, a joint patrol of Iraqi and U.S. forces discovered and dismantled a fourth car bomb before it exploded, Iraqi authorities said.

The 2009 pickup truck, parked outside a Green Zone gate, was packed with seven bombs that were covered by blankets and cartons, said an Interior Ministry official and a Baghdad police officer. Both spoke on condition of anonymity because they were not authorized to speak to the media.

The U.S. military said it would send forensic and explosive experts to help Iraqi authorities investigate the bombings in Baghdad. Army Lt. Brian Wierzbicki, a U.S. military spokesman did not have any immediate reports of casualties.

No one immediately claimed responsibility for the bombings. Insurgent groups associated with Al Qaeda have claimed responsibility for the earlier bombings, although al-Maliki also has blamed loyalists of former dictator Saddam Hussein.

The attacks have raised serious questions about the abilities of Iraqi security forces ahead of the U.S. withdrawal of combat troops. The American military has warned of a possible rise in violence with insurgents hoping to destabilize the government ahead of the March 7 parliamentary elections.

On Monday, Iraqi Defense Minister Abdul-Qader al-Obeidi acknowledged shortcomings in the security forces but said insurgents have changed their tactics amid the U.S. troop withdrawal.

"The nature of terrorism has changed, and terrorists are conducting attacks that aim to inflict the largest casualties," al-Obeidi said.

He did not indicate what he meant by changing tactics. However, much of the recent violence has targeted government institutions, as opposed to violence that appeared designed to spark Shiite-Sunni tensions.

The U.S. has pinned the pace of its withdrawal of combat troops by Aug. 31, 2010.