BAGHDAD – Attackers unleashed a carefully planned assault with car bombs and gunmen disguised as police on the Iraqi Justice Ministry on Thursday, killing at least 24 people as hundreds of others crouched terrified in their offices.

The large and complex raid in the heart of downtown Baghdad came less than a week before the 10th anniversary of the U.S.-led invasion of Iraq, showing how vulnerable this country remains to insurgent attacks.

The fighting lasted about an hour, ending with security forces storming the four-story building after some of the gunmen detonated suicide vests, according to police and witnesses. None of the attackers survived.