Tuesday's early morning attacks appeared coordinated and aimed at checkpoints manned by members of Iraq's fledgling army, which has been a constant target of fighters opposed to the country's new government.
The first explosion, caused by a roadside bomb, rocked Hawija, about 65km south of Kirkuk, at around 9.30am, killing three civilians, Brigadier-General Anwar Mohammed Amin said.
Heavily armed US soldiers sealed off the bomb scene, allowing only ambulances to enter and reach the dead and wounded.
Three car bombers then struck in quick succession, attacking in Bagara, Dibis and at the entrance to Hawija. Amin said three soldiers were killed in the Bagara bombing.
Casualties from the morning attacks, including 18 wounded, were transported to the main hospitals in Hawija and the provincial capital Kirkuk, said Yarub al-Sumaidi, a medic in Hawija's general hospital.
US forces sealed the town and Apache attack helicopters patrolled overhead.
A new car bombing in Baghdad on Tuesday wounded 28 people, shattering the relative calm of recent days as Iraqi forces backed by US troops pressed a sweep dubbed Operation Lightning.
The blast hit a police patrol in the predominantly Shia Shula district in northern Baghdad, an interior ministry official said.
Abu Ghraib riots
Also on Tuesday, relatives of a Sunni Muslim cleric in the southern Iraqi city of Basra said he had been killed.
His is the latest in a series of assassinations of religious figures that have stoked sectarian tensions.
Guards and detainees were
injured in Abu Ghraib rioting
Witnesses said Salam Abd al-Karim was taken from his home on Sunday by men in police uniform. His body was found the following day.
Last week, the imam of a Shia mosque was also assassinated in Basra.
In a separate incident, the Shaikh of al-Buthaneen tribe, Hussain Abd al-Hadi, and his driver came under attack while in his car at Abu Tayara street in Dora area, Iraqi journalist Walid Khalid reported.
He was transferred to al-Yarmuk hospital and is now in a very critical condition, the journalist added.
Elsewhere, two US marines died as a result of separate roadside bombings near the western Iraqi city of Falluja, the US military said on Tuesday.
One marine was killed in action on Monday when a bomb targeted his vehicle near Falluja, 65km west of Baghdad, the military said in a statement.
Another marine was seriously wounded on Sunday and died a day later also near Falluja in a similar incident.
Both marines were assigned to Regimental Combat Team-8, 2nd Marine Division, II Marine Expeditionary Force.
The names of the marines are being withheld pending next-of-kin notification.
Meanwhile, several guards and detainees were injured after rioting erupted in the notorious US-run prison of Abu Ghraib on Baghdad's western outskirts after a detainee tried to escape.
"The disturbance occurred shortly after a detainee, using the hours of darkness and a heavy sandstorm, was caught trying to escape," the US military said in a statement on Tuesday.
"Detainees in several of the compounds began throwing rocks at the portable light generators and the guards"
US military statement
"Detainees in several of the compounds began throwing rocks at the portable light generators and the guards," it said.
The US military said the incident occurred on Sunday shortly before midnight.
Four guards and six detainees were injured and treated at the scene.
All detainees were accounted for after the disturbance ended, the statement added, without providing further details.
In May, three detainees escaped from Abu Ghraib, the scene of abuse of Iraqi prisoners by their US warders captured in graphic photographs that made headlines around the world in April last year.
Speaking to Aljazeera, General Wafiq al-Samarraey, security adviser to the Iraqi president, said fighters were starting to target each other.
"In western Iraq, clashes have erupted between al-Qaida organisation and the so-called Ansar al-Sunna on one hand and the remnants of Saddam loyalists and the so-called Jaish Muhammad on the other.
"The leader of the so-called Jaish Muhammad was killed in Hiyt district while the fighting was still raging," he said.
"This is a clear indication that the pressure exerted by the government and by the Iraqi people has borne fruit and the terrorists are fighting one another."
Despite the day's attacks, he said he thought the government's strategy was working.
Iraqi soldiers have been advised
not to group at control sites
"Suicide operations often leave distinct psychological, moral and publicity impressions. But they (the terrorists) are incapable of waging an open-ended war.
"We are assured that security is making steady progress. I am assured at both personal and national levels that terrorist operations have subsided within the last three months, as compared to the previous three month period. The drop is at the rate of 100 terrorist operations per week, and that is a big drop."