BAGHDAD - At least 20 people were killed and 35 wounded in bombings and shootings in Iraq on Wednesday, police and medical sources said, the latest in a string of attacks that threaten to tilt the country back into all-out sectarian warfare.Four suicide bombers targeted a police station in Ramadi, west of Baghdad, killing four policemen and wounding 15. Another attacked a police station just north of Ramadi, killing four officers and wounding seven, the sources said.A roadside bomb targeted an Iraqi army patrol in the western city of Qaim on the Iraqi-Syrian border. One soldier was killed and another wounded, police said.