"What crime have we committed? Children and women were buried under debris. Why did the Iraqi troops let this car bomb pass? Why didn't they discover it by explosive detector."

The attacks offer a brutal reminder that insurgency is far from over. And more targets are being added to the assault checklist.

The first car packed with explosives detonated close to the Labor Ministry Building, the next near the Iraqi-protected Green Zone, and the last by the Finance Ministry.

Observers say this marks a change of tactics by Iraq's extremists. They are shifting from soft targets, like crowded markets, to the more spectacular lure of heavily defend government buildings.

No group has claimed responsibility yet but, considering the timing of the blasts, many believe the perpetrators are seeking to discredit the government of Prime Minister Nouri Al-Maliki ahead of next year's parliamentary elections.