Aug. 16: Shiite pilgrims gather in front of the Shrine of Imam Abbas in Karbala, Iraq. A car bomb struck Shiite pilgrims boarding minibuses in Baghdad Saturday, killing at least six people as they were heading to the Shabaniyah festival in Karbala, which ends this weekend and marks the birth of Mohammed al-Mahdi, the 12th Shiite imam who disappeared in the 9th century.