Both bombs, which went off about two hours apart on Sunday, exploded near crowded bus stations in a seemingly coordinated effort.
Iraqi medical sources said about 48 Iraqi civilians were killed and another 90 wounded in the car-bombing in Najaf, while the explosion that rocked Karbala killed 16 Iraqi civilians and wounded 56 others, Aljazeera reported. Additionally, there have been scores of casualties from clashes in other Iraqi cities.
Earlier in the day, anti-interim government fighters killed three Iraqi electoral commission employees after hauling them from a car on a busy street in Baghdad.
The car bomb blasts were not far from the Imam Ali mosque in Najaf and Imam Husain mosque in Karbala, revered by Muslims in general and Shia Muslims in particular. The sect's leaders have called on their people not to seek revenge.
In Najaf, the bomber detonated his vehicle about 300 yards from the Imam Ali shrine, near crowds of people queuing for buses and taxis and not far from busy offices.
The explosion left stunned crowds waiting in freezing temperatures for ambulances. A thick column of smoke rose from the blast site as rare drizzling rain fell.
Sunday's blast was the second to
strike Karbala city in five days
In Karbala, an official at the main hospital said all the victims appeared to be civilians and there were many women and children among them.
Speaking to Aljazeera from the city, Husain al-Shimri, an Iraqi journalist, said the explosion left body parts scattered everywhere.
The impact of the blast was such that the bodies transferred to the main hospital were little more than lumps of flesh. "It was a slaughter," he said.
"Families of the injured who gathered outside Karbala general hospital were panic-stricken."
According to al-Shimri, the blasts appeared to have targeted civilians since they occurred in residential places where there were no US military posts or Iraqi police stations.
The Karbala attack was the second in five days. On Wednesday, a bomb apparently targeting Shia cleric Abd Al-Mahdi al-Karbalai exploded as he was returning to his office after evening prayers at the Imam Husain shrine.
Poll officers killed
Separately, on Friday and Saturday, three election offices were attacked in the north. In Baghdad, armed men dragged three junior electoral commission employees from a car and shot them dead.
The blasts destroyed vehicles and
left the scene strewn with bodies
It was not clear if they were targeted because they worked for the electoral body, a commission spokesman said.
Witnesses said the assailants opened fire on the vehicle before dragging out and shooting three passengers. Two other electoral workers escaped the early morning attack.
Separately, four Kurds were killed by unknown assailants in Hawija, southwest of the ethnically tense city of Kirkuk. Two other Kurds were killed in another attack nearby last week.
In other developments, anti-US fighters are threatening to kill 10 Iraqis employed by a US security company unless the firm pulls out of Iraq, a caller from the captors told Reuters. Arab satellite channels broadcast a tape showing the captives.
It was not clear when the men were seized. No deadline appears to have been set for the threats to be carried out.