At least 72 people have been killed in a coordinated wave of attacks across Iraq targeting Shi'ite Muslim pilgrims gathered for annual religious processions. Nearly 260 others were wounded, in one of the bloodiest days since U.S. troops withdrew from the country.

Most of the bombs exploded in Baghdad and the southern Iraqi cities of Hilla, Karbala and Haswa – predominantly Shi'ite areas that have been targeted before by Sunni Islamist insurgents.

The pilgrims were marking the anniversary centuries ago of the death of the revered Shi'ite Imam Moussa al-Kadhim.

Explosions also targeted Iraqi Kurds in the north.

The pilgrimage culminates on Saturday, raising the prospect of further violence in the coming days.

The latest bombings and shootings also coincide with an Iraqi political crisis in which minority Sunni and Kurdish lawmakers have been trying to unseat Shi'ite Prime Minister Nouri al-Maliki, accusing him of monopolizing power in Shi'ite hands.

Baghdad's central government is also caught in a long-running fight with the autonomous Kurdistan region over disputed land and oil claims.

The targeting of Shi'ite pilgrims was a common tactic during the vicious civil war that tore Iraq apart in 2006 and 2007 and was condemned by parliament speaker Osama al-Nujaifi, who termed it an attempt “to provoke sectarian strife.”

Violence in Iraq has declined since then, but attacks remain common, especially in Baghdad.

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