Two suicide car bombs exploded in downtown Baghdad on Sunday, killing at least 136 people and delivering a powerful blow to the heart of the fragile city's government in the worst attack of the year, officials said.

 Black smoke could be seen billowing from the frantic scene, as emergency service vehicles sped to the area. Even civilian cars were being commandeered to transport the wounded to hospitals.

"The walls collapsed and we had to run out,'' said Yasmeen Afdhal, 24, an employee of the Baghdad provincial administration, which was targeted by one of the car bombs. "There are many wounded, and I saw them being taken away. They were pulling victims out of the rubble, and rushing them to ambulances".

The car bombs, which targeted the justice ministry and the Baghdad provincial administration, come as Iraq is preparing for elections scheduled this January.

 There have been no claims of responsibility so far, but massive car bombs have been the hallmark of the Sunni insurgents seeking to overthrow the country's Shia-dominated government. At least 25 members of the Baghdad Provincial Council, which runs the city, were killed in the blast.

 The area where the blasts occurred is just a few hundred yards from the Green Zone that houses the US embassy as well as the PM's offices. The street where the blasts occurred had just been reopened to vehicle traffic a few months ago, in what was supposed to be a sign that safety was returning to the once devastated city.

The explosive-laden vehicles were sitting in parking garages next to the two government building, police said. "This is a political struggle, the price of which we are paying,'' said provincial council member Mohammed al-Rubaiey. "Every politician is responsible and even the government is responsible, as well as security leaders.''