Minutes later, a roadside bomb struck a car on a highway on the western outskirts of Tikrit, 80 miles north of Baghdad, killing two civilians and wounding two others, police said.
The first blast occurred about 8 a.m. as police were arriving for work at the Adwar police station, provincial police Capt. Abdel-Samad Mohammed said, giving the casualty toll. He said 21 of the 30 killed were policemen.
The bomber drove a small truck that was packed with explosives covered by hay and the force of the blast caused the building to collapse. Three houses close to the station, along with municipal offices and the post office, also were heavily damaged.
Local residents who rushed to the scene tried to help with rescue efforts before civil defense squads arrived with shovels to remove the debris and pull out the dead and those injured. U.S. and Iraqi forces later surrounded the area while recovery efforts continued.
Adwar, about 12 miles southeast of Tikrit, is where former Iraqi leader Saddam Hussein was captured on Dec. 13, 2003.
Insurgents frequently target Iraqi security forces, accusing them of collaborating with the U.S.