At least 12 people have been killed and dozens injured in a powerful suicide car bombing in Baghdad. The bomb exploded in the center of a busy commercial district during morning rush hour, setting vehicles on fire and destroying nearby shops and buildings.

Dozens of Iraqis swarm the site of a severely damaged apartment building, trying desperately to find people trapped underneath huge mounds of debris.

A few meters away, an ambulance carrying several critically wounded Iraqis tries to maneuver its way through a haze of thick smoke from burning vehicles and chunks of metal littering the street.

The apartment building in Tahir Square in the center of Baghdad was ripped apart, along with several shops nearby, by a blast so powerful, it shook buildings several kilometers away. A witness, who does not want to be identified, says he saw the driver of a red, four-wheel-drive vehicle behaving suspiciously just before he blew up the car.

The witness says the driver of the red car weaved through traffic toward three sports-utility vehicles carrying Westerners. He then saw all the vehicles explode at once.

Iraqi Interim Prime Minister Iyad Allawi told reporters the suicide bomber targeted Western electrical engineers in the convoy. He said five Westerners, including one French and two British citizens, were killed and three others lightly wounded.

Foreign contractors often travel in sports-utility vehicles, which frequently come under attack by passing cars.

The blast was the second suicide bombing in the Iraqi capital in 24 hours and the 17th car bombing this month. The violence also coincides with a wave of assassinations and attempted assassinations in the past week, aimed at interim government officials.

Prime Minister Allawi blamed the violence on terrorists, whom he says are trying to prevent the official transfer of power and sovereignty to an Iraqi government on June 30.