BAGHDAD, Iraq - Two car bombs exploded in a main square of central Baghdad on Tuesday morning, killing at least 57 people and wounding 106, police said.

Burnt vehicles lie at the scene of a car bomb attack in a parking lot of Mahmoun University in Baghdad December 11, 2006. The attack killed one person and wounded four others, including two policemen. [AP]

The carefully coordinated attack in Tayaran Square at 7 a.m. involved a bomb in a parked car and a suicide car bomb, both of which exploded simultaneously near a police patrol and a crowd of Iraqis gathering to apply for jobs as day laborers, said police Lt. Bilal Ali.

He said at least 57 Iraqis, including seven policemen, were killed and 104 people wounded.

Gunfire could be heard right after the explosions, which occurred about 100 feet apart, but it was not immediately known if it involved police or insurgent snipers hiding nearby, Ali said.

In Baghdad, where many people are unemployed, scores of Iraqis gather in the square early in the morning to wait for minibuses or private cars that stop by and hire them for the day as construction workers, cleaners or painters. Nearby, small stands are set up to sell the laborers a breakfast of tea and egg sandwiches.

The suicide car bomber appeared to drive into one of those crowds and set off his explosives as the nearby parked car bomb also went off, Ali said.

Khalil Ibrahim, 41, a shop owner in the area, said: "In the first explosion, I saw people falling over, some of them blown apart. When the other bomb went off seconds later, it slammed me into a wall of my store and I fainted." He was speaking from a local hospital where he had been taken to be treated for shrapnel wounds to his head and back.

Tayaran Square is located near several government ministries and a bridge that crosses the Tigris River to the heavily fortified Green Zone, where Iraq's parliament and the US and British embassies are located.