There were no women among them.
The detention of Iraqi women has become a contentious issue, particularly since the kidnapping on 7 January of the U.S. journalist Jill Carroll. Her kidnappers have threatened to kill her unless all Iraqi women are freed from custody.
In other news, Iraqi police say they found the bodies of two men who had been shot dead and dumped north of Baghdad.
Police said the victims were wearing black clothes and appeared to be Shias preparing for the religious festival of Ashura, which begins on 8 January.