A bomb hidden in a plastic bag near a Shiite shrine on Wednesday killed seven people and wounded 23, including women and children, in the third straight day of attacks in Baghdad, officials said. The mid-morning explosion occurred at a security checkpoint only 200 metres (yards) from the Musa Kadhim mosque, security officials told a foreign news agency. "The bomb was inside a bag filled with screws and nails," said a police official, asking not to be identified. "(The attacker) couldn't pass one of the checkpoints to take the bomb to the nearest place to the shrine, so he left it in that place and ran away." Shiite Islam's most important house of prayer in the Iraqi capital has been the scene of repeated attacks since the 2003 US-led invasion to topple Saddam Hussein triggered deadly sectarian violence. Yasser Abdul Hussein, a shop owner whose goods were damaged and scattered by the force of the blast, said: "Someone came and placed the bag in the street. We don't know if it was a man or a woman. They ran away immediately."