Another 41 policemen were wounded in the explosion, which struck in the centre of the city at around 7:00 am (0400 GMT), according to a police major and an official in the city's health department, both of whom spoke on condition of anonymity.
Among the dead were a police captain and a first lieutenant. There were also three officers among the wounded. The explosion badly damaged the facade and several sections of the police station, which houses the emergency-response brigade, and left a crater two metres (more than six feet) in diameter.
Several nearby houses and shops were also seriously damaged, an AFP journalist said. Security forces have since cordoned off the blast site. Mainly Shiite Hilla lies just beyond the edge of a confessionally mixed area south of the capital that earned the monicker Triangle of Death during the sectarian bloodshed that peaked in Iraq in 2006 and 2007.
Over the years it has been repeatedly bombed by insurgents loyal to al Qaeda leader Osama bin Laden, whose death in a US special forces raid in Pakistan President Barack Obama announced in a White House address late on Sunday.
Violence is down dramatically in Iraq from its peak, but attacks remain common. A total of 211 Iraqis were killed in violence in April, according to official figures.
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