Sunday police found bodies of three men — bound, blindfolded and shot execution-style — in Baghdad's Shiite stronghold of Sadr City. They appeared to be the latest victims of sectarian tit-for-tat killings, which have sharpened religious tensions as Iraqi politicians try to form a national unity government following the December parliamentary elections. The Interior Ministry has announced an investigation into allegations of Shiite death squads in police ranks after U.S. troops arrested 22 policemen preparing to kill a Sunni Arab last month.