A coordinated wave of car bombs struck Shiite pilgrims in Baghdad and several other cities Wednesday, killing at least 65 people and wounding more than 200 in one of the deadliest days in Iraq since U.S. troops withdrew from the country.

The bloodshed comes against a backdrop of political divisions that have raised tensions and threatened to provoke a new round of the violence that once pushed Iraq to the brink of civil war. Nobody immediately claimed responsibility for the attacks, but they bore the hallmarks of Sunni insurgents who frequently target Shiites in Iraq.

Wednesday's blasts were the third this week targeting the annual pilgrimage that sees hundreds of thousands of Shiites converge on a golden-domed shrine in Baghdad's northern neighborhood of Kazimiyah to commemorate the eighth century death of a revered Shiite saint, Imam Moussa al-Kadhim. The commemoration culminates on Saturday.