Iraqi police say a bomb has exploded in central Baghdad killing four people and wounding eight. The police say the roadside bomb exploded near the downtown Tayaran Square. A police officer says the 11:20 a.m. blast missed a police patrol but hit a passing minibus. The officer asked not to be identified because he is not authorized to speak to the media. Monday's explosion was one in a series of attacks on security forces in Baghdad in the past two weeks. Dozens have died in the daily clashes with Shiite militants in the capital's eastern districts.