A suicide car bomber killed at least five people and wounded 15 in an attack on an Iraqi police headquarters in the northern town of Tikrit, police sources said.
Men volunteering to join the force had been crowding the area at the time, they added.
Tikrit is the home town of former Iraqi leader Saddam Hussein and lies in the heartlands of the once dominant Sunni Arab minority, some of whom have risen against the new Shi'ite-led government and the US military occupation.
Suicide attacks have been a frequent tactic against Iraq's police and army recruits, who form a key part of Washington's strategy for withdrawing many of its own troops.