Scores of people have been killed in a series of bomb blasts which ripped through the Shiite neighbourhoods of the Iraqi capital Baghdad.

At least 70 people have been reported dead so far, after more than a dozen blasts decimated markets and shopping areas across the capital.

One of the car bombs exploded when the police officials were waiting for bomb experts to defuse the explosives. Security forces were also injured in the explosion.

"A driver hit another car and left pretending to bring traffic police. Another car rushed to take him away and right after his car exploded among people who had gathered to see what was happening. People were shouting for help and blood covered their faces," an onlooker named Hassan Kadhim told Reuters.

Firefighters were seen struggling to extinguish flames across areas, as the US diplomatic mission in Iraq spoke out in condemnation of the attack.

No one has officially claimed responsibility, but the wave of car bombings bears a striking resemblance to the attacks which took place across Baghdad just days previously.

Sunni-dominated Islamic militant groups have also stepped up their attacks on the Shiite neighbourhoods, and al-Qaida are reportedly playing an increasingly prominent role.

More than 350 people have been killed in the last two weeks, as Iraq becomes increasingly mired in sectarian violence - a problem exacerbated by the civil war in neighbouring Syria.

The Shiite-led government has been struggling hard to combat the Sunni insurgents ever since American troops left the country at the end of 2011.

The recent upsurge in the sectarian conflict gives a grim reminder of earlier violence which pushed the country to the brink of civil war in 2006.

Civilians inspect the scene of a car bomb attack in Baghdad's Sadr City - Reuters
A woman walks near the site of the car bomb attack in Baghdad's Sadr CityReuters
Civilians inspect the scene of a car bomb attack in Baghdad's Sadr CityReuters
Civilians inspect the scene of a car bomb attack in Baghdad's Sadr CityReuters
A man reacts at the site of a car bomb attack in Baghdad's Sadr CityReuters
Residents gather at the site of a car bomb attack in Baghdad's Sadr CityReuters