Sporadic clashes also erupted between armed fighters and US troops in other parts of Ramadi on Wednesday, but no details about casualties or losses were available.
Later at night, a powerful roadside bomb exploded in downtown Baghdad as an Iraqi police patrol truck was driving past, wounding three policemen and a civilian who was walking on a nearby sidewalk, an official said.
The police truck was thrown 10 metres and severely damaged by the blast. One of the wounded policemen was taken to hospital with serious injuries, police Lt Uthman Abd al-Sattar said.
Earlier in the day, at least two Iraqis were killed and several other people were wounded in two car bombings that occurred within 90 minutes of each other and in two drive-by shootings, an Interior Ministry official said.
One of the car bombs exploded near a US convoy in western Baghdad where Abu Ghraib prison is, setting an oil tanker on fire, police Major Musa Abd al-Karim said.
Anti-US and anti-government
fighters are stepping up attacks
Muhammad Abd Allah, an Iraqi journalist, told Aljazeera a US military vehicle was destroyed and a number of civilians were injured in the attack.
US forces cordoned off the explosion site, preventing anyone, including reporters, from approaching, he said.
In Sadr City in eastern Baghdad, armed men in a speeding car opened fire on police officer Ali Talib as he walked towards his car, killing him, police Colonel Husain Abd al-Wahid said.
In eastern Baghdad, a Health Ministry car was attacked by armed men, killing the Iraqi driver and wounding one unidentified passenger, police Colonel Hasan Jalub said.
US soldiers killed
In the southern city of Basra, where most of the British forces in Iraq are based, Abd al-Batat, a former aide to Saddam Hussein's half brother, Sabawi Ibrahim al-Hasan, was killed on Tuesday when fighters opened fire on him outside his home, police Lt-Col Karim al-Zaydi said.
On Tuesday night, an attack by a car bomber near an American patrol in southern Baghdad killed two US soldiers and wounded four, Lieutenant-Colonel Clifford Kent, a spokesman for the US 3rd Infantry Division, said on Wednesday.
In many operations, US forces
are backing up Iraqi soldiers
The explosion occurred in Baghdad's al-Amil area.
Seven Iraqi civilians also were taken to Yarmuk Hospital with injuries, an official said on Wednesday.
It was one of a series of attacks by fighters in Iraq on Tuesday, which killed a dozen other Iraqis and wounded more than 60.
Meanwhile, the US military has said it regretted an incident in which an Iraqi legislator said an American soldier handcuffed and humiliated him, but it found after an initial investigation a differing version of the event.
Tuesday's scuffle involving US troops and Fatah al-Shaikh, a legislator loyal to Shia cleric Muqtada al-Sadr, occurred as al-Shaikh arrived for a parliamentary session in Baghdad's fortified Green Zone.
On Wednesday, Aljazeera aired an interview with Iraqi writer and journalist Hani Ashur on the upsurge in violence. Asked to explain the reason behind the escalation, he attributed it to the stuttering political process, including the long delay in government formation.
Ashur said the new government had clear obligations to the people, such as providing services and security and debating the constitution. Any delay in meeting these commitments might act as a trigger for more violence.
Arrests of anti-US fighters have
failed to crush their campaign
Also, it is worth noting that the recent attacks have focused more or less on the same targets. In Haditha, for example, the town's police commander and other senior officers were killed a few days ago, to be followed by the killing of several Iraqi soldiers. This indicated that the security measures taken in Haditha were ineffective.
By contrast, the assailants demonstrated the capability to manoeuvre from one area of operation to another with ease, making use of superior techniques and means of communication and transportation to strike at a chosen target in an organised manner.
Climate of insecurity
Asked how the anti-government attacks could be linked to the political process, given that the fighters do not recognise the process, Ashur said the long-drawn-out process marking government formation had led to a climate of anxiety and insecurity, which had been exploited by the attackers.
The depressing pace of the political process coupled with the pervasive presence of US forces has convinced many Iraqis that they have lost sovereignty and political independence.
Deadly car bombings epitomise
life in newly democratic Iraq
Unsurprisingly, many deputies are calling for the withdrawal of US troops in the hope that this will put an end to the seemingly endless cycle of violence.
Finally, questioned on the reason behind the latest anti-Iranian protests in many areas, Ashur said these were a result of what happened in al-Madain recently, together with the statements made by Iraqi officials alleging Iranian involvement in the standoff.
"What we are seeing today is an expression of the masses' yearning for peace and stability, as also the resolution of all outstanding problems facing Iraq," he said.