Police say the attack sent many of the mortar rounds into the court house and residential communities.
In other violence, a police commander's convoy was struck by a roadside bomb in the town of Hamzah, south of Baghdad, killing two guards.
Another roadside bomb in Baghdad's Shi'ite neighborhood of Sadr City killed one civilian.
RFE/RL Iraq Report
SUBSCRIBE For weekly news and analysis on Iraq by e-mail, subscribe to "RFE/RL Iraq Report."